Op crate for Web APIs (#6906)

Co-authored-by: Ryan Dahl <ry@tinyclouds.org>

19 files changed, 1159 insertions, 344 deletions

diff --git a/Cargo.lock b/Cargo.lock
index a43eda71d..80f43a6eb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -382,6 +382,7 @@ dependencies = [
  "clap",
  "deno_core",
  "deno_lint",
+ "deno_web",
  "dissimilar",
  "dlopen",
  "dprint-plugin-typescript",
@@ -460,6 +461,14 @@ dependencies = [
 ]
 
 [[package]]
+name = "deno_web"
+version = "0.1.0"
+dependencies = [
+ "deno_core",
+ "futures",
+]
+
+[[package]]
 name = "derive_deref"
 version = "1.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/Cargo.toml b/Cargo.toml
index b89523628..80e6ce4e6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,6 +4,7 @@ members = [
   "core",
   "test_plugin",
   "test_util",
+  "op_crates/web",
 ]
 exclude = [
   "std/hash/_wasm"
diff --git a/cli/Cargo.toml b/cli/Cargo.toml
index 8a8958b63..bedbdb657 100644
--- a/cli/Cargo.toml
+++ b/cli/Cargo.toml
@@ -16,6 +16,7 @@ path = "main.rs"
 
 [build-dependencies]
 deno_core = { path = "../core", version = "0.51.0" }
+deno_web = { path = "../op_crates/web", version = "0.1.0" }
 
 [target.'cfg(windows)'.build-dependencies]
 winres = "0.1"
diff --git a/cli/build.rs b/cli/build.rs
index 777e74558..5a7f173e5 100644
--- a/cli/build.rs
+++ b/cli/build.rs
@@ -38,6 +38,11 @@ fn create_compiler_snapshot(
 ) {
   let mut runtime_isolate = CoreIsolate::new(StartupData::None, true);
   let mut custom_libs: HashMap<String, PathBuf> = HashMap::new();
+  let web_scripts = deno_web::get_scripts();
+  custom_libs.insert(
+    "lib.deno.web.d.ts".to_string(),
+    PathBuf::from(web_scripts.declaration),
+  );
   custom_libs.insert(
     "lib.deno.window.d.ts".to_string(),
     cwd.join("dts/lib.deno.window.d.ts"),
@@ -80,6 +85,10 @@ fn main() {
   // op_fetch_asset::trace_serializer();
 
   println!("cargo:rustc-env=TS_VERSION={}", ts_version());
+  println!(
+    "cargo:rustc-env=DENO_WEB_LIB_PATH={}",
+    deno_web::get_scripts().declaration
+  );
 
   println!(
     "cargo:rustc-env=TARGET={}",
@@ -93,7 +102,7 @@ fn main() {
   let runtime_snapshot_path = o.join("CLI_SNAPSHOT.bin");
   let compiler_snapshot_path = o.join("COMPILER_SNAPSHOT.bin");
 
-  let js_files = get_js_files("rt");
+  let js_files = get_js_files_for_rt();
   create_runtime_snapshot(&runtime_snapshot_path, js_files);
 
   let js_files = get_js_files("tsc");
@@ -123,3 +132,67 @@ fn get_js_files(d: &str) -> Vec<String> {
   js_files.sort();
   js_files
 }
+
+fn get_js_files_for_rt() -> Vec<String> {
+  let web_scripts = deno_web::get_scripts();
+
+  let f = vec![
+    "rt/00_bootstrap_namespace.js",
+    &web_scripts.dom_exception,
+    "rt/01_build.js",
+    "rt/01_colors.js",
+    "rt/01_errors.js",
+    &web_scripts.event,
+    "rt/01_internals.js",
+    "rt/01_version.js",
+    "rt/01_web_util.js",
+    "rt/02_abort_signal.js",
+    "rt/02_console.js",
+    "rt/03_dom_iterable.js",
+    "rt/06_util.js",
+    &web_scripts.text_encoding,
+    "rt/10_dispatch_json.js",
+    "rt/10_dispatch_minimal.js",
+    "rt/11_crypto.js",
+    "rt/11_resources.js",
+    "rt/11_streams.js",
+    "rt/11_timers.js",
+    "rt/11_url.js",
+    "rt/11_workers.js",
+    "rt/12_io.js",
+    "rt/13_buffer.js",
+    "rt/20_blob.js",
+    "rt/20_headers.js",
+    "rt/20_streams_queuing_strategy.js",
+    "rt/21_dom_file.js",
+    "rt/22_form_data.js",
+    "rt/23_multipart.js",
+    "rt/24_body.js",
+    "rt/25_request.js",
+    "rt/26_fetch.js",
+    "rt/30_files.js",
+    "rt/30_fs.js",
+    "rt/30_metrics.js",
+    "rt/30_net.js",
+    "rt/30_os.js",
+    "rt/40_compiler_api.js",
+    "rt/40_diagnostics.js",
+    "rt/40_error_stack.js",
+    "rt/40_fs_events.js",
+    "rt/40_net_unstable.js",
+    "rt/40_performance.js",
+    "rt/40_permissions.js",
+    "rt/40_plugins.js",
+    "rt/40_process.js",
+    "rt/40_read_file.js",
+    "rt/40_repl.js",
+    "rt/40_signals.js",
+    "rt/40_testing.js",
+    "rt/40_tls.js",
+    "rt/40_tty.js",
+    "rt/40_write_file.js",
+    "rt/90_deno_ns.js",
+    "rt/99_main.js",
+  ];
+  f.iter().map(|p| p.to_string()).collect()
+}
diff --git a/cli/dts/lib.deno.shared_globals.d.ts b/cli/dts/lib.deno.shared_globals.d.ts
index e331baee1..ec5367962 100644
--- a/cli/dts/lib.deno.shared_globals.d.ts
+++ b/cli/dts/lib.deno.shared_globals.d.ts
@@ -4,6 +4,7 @@
 
 /// <reference no-default-lib="true" />
 /// <reference lib="esnext" />
+/// <reference lib="deno.web" />
 
 // This follows the WebIDL at: https://webassembly.github.io/spec/js-api/
 // and: https://webassembly.github.io/spec/web-api/
@@ -529,12 +530,6 @@ interface DOMStringList {
   [index: number]: string;
 }
 
-declare class DOMException extends Error {
-  constructor(message?: string, name?: string);
-  readonly name: string;
-  readonly message: string;
-}
-
 type BufferSource = ArrayBufferView | ArrayBuffer;
 type BlobPart = BufferSource | Blob | string;
 
@@ -1030,46 +1025,6 @@ declare function fetch(
   init?: RequestInit,
 ): Promise<Response>;
 
-/** Decodes a string of data which has been encoded using base-64 encoding.
- *
- *     console.log(atob("aGVsbG8gd29ybGQ=")); // outputs 'hello world'
- */
-declare function atob(s: string): string;
-
-/** Creates a base-64 ASCII encoded string from the input string.
- *
- *     console.log(btoa("hello world"));  // outputs "aGVsbG8gd29ybGQ="
- */
-declare function btoa(s: string): string;
-
-declare class TextDecoder {
-  /** Returns encoding's name, lowercased. */
-  readonly encoding: string;
-  /** Returns `true` if error mode is "fatal", and `false` otherwise. */
-  readonly fatal: boolean;
-  /** Returns `true` if ignore BOM flag is set, and `false` otherwise. */
-  readonly ignoreBOM = false;
-  constructor(
-    label?: string,
-    options?: { fatal?: boolean; ignoreBOM?: boolean },
-  );
-  /** Returns the result of running encoding's decoder. */
-  decode(input?: BufferSource, options?: { stream?: false }): string;
-  readonly [Symbol.toStringTag]: string;
-}
-
-declare class TextEncoder {
-  /** Returns "utf-8". */
-  readonly encoding = "utf-8";
-  /** Returns the result of running UTF-8's encoder. */
-  encode(input?: string): Uint8Array;
-  encodeInto(
-    input: string,
-    dest: Uint8Array,
-  ): { read: number; written: number };
-  readonly [Symbol.toStringTag]: string;
-}
-
 interface URLSearchParams {
   /** Appends a specified key/value pair as a new search parameter.
    *
@@ -1444,143 +1399,6 @@ declare class PerformanceMeasure extends PerformanceEntry {
   readonly entryType: "measure";
 }
 
-interface EventInit {
-  bubbles?: boolean;
-  cancelable?: boolean;
-  composed?: boolean;
-}
-
-/** An event which takes place in the DOM. */
-declare class Event {
-  constructor(type: string, eventInitDict?: EventInit);
-  /** Returns true or false depending on how event was initialized. True if
-   * event goes through its target's ancestors in reverse tree order, and
-   * false otherwise. */
-  readonly bubbles: boolean;
-  cancelBubble: boolean;
-  /** Returns true or false depending on how event was initialized. Its return
-   * value does not always carry meaning, but true can indicate that part of the
-   * operation during which event was dispatched, can be canceled by invoking
-   * the preventDefault() method. */
-  readonly cancelable: boolean;
-  /** Returns true or false depending on how event was initialized. True if
-   * event invokes listeners past a ShadowRoot node that is the root of its
-   * target, and false otherwise. */
-  readonly composed: boolean;
-  /** Returns the object whose event listener's callback is currently being
-   * invoked. */
-  readonly currentTarget: EventTarget | null;
-  /** Returns true if preventDefault() was invoked successfully to indicate
-   * cancellation, and false otherwise. */
-  readonly defaultPrevented: boolean;
-  /** Returns the event's phase, which is one of NONE, CAPTURING_PHASE,
-   * AT_TARGET, and BUBBLING_PHASE. */
-  readonly eventPhase: number;
-  /** Returns true if event was dispatched by the user agent, and false
-   * otherwise. */
-  readonly isTrusted: boolean;
-  /** Returns the object to which event is dispatched (its target). */
-  readonly target: EventTarget | null;
-  /** Returns the event's timestamp as the number of milliseconds measured
-   * relative to the time origin. */
-  readonly timeStamp: number;
-  /** Returns the type of event, e.g. "click", "hashchange", or "submit". */
-  readonly type: string;
-  /** Returns the invocation target objects of event's path (objects on which
-   * listeners will be invoked), except for any nodes in shadow trees of which
-   * the shadow root's mode is "closed" that are not reachable from event's
-   * currentTarget. */
-  composedPath(): EventTarget[];
-  /** If invoked when the cancelable attribute value is true, and while
-   * executing a listener for the event with passive set to false, signals to
-   * the operation that caused event to be dispatched that it needs to be
-   * canceled. */
-  preventDefault(): void;
-  /** Invoking this method prevents event from reaching any registered event
-   * listeners after the current one finishes running and, when dispatched in a
-   * tree, also prevents event from reaching any other objects. */
-  stopImmediatePropagation(): void;
-  /** When dispatched in a tree, invoking this method prevents event from
-   * reaching any objects other than the current object. */
-  stopPropagation(): void;
-  readonly AT_TARGET: number;
-  readonly BUBBLING_PHASE: number;
-  readonly CAPTURING_PHASE: number;
-  readonly NONE: number;
-  static readonly AT_TARGET: number;
-  static readonly BUBBLING_PHASE: number;
-  static readonly CAPTURING_PHASE: number;
-  static readonly NONE: number;
-}
-
-/**
- * EventTarget is a DOM interface implemented by objects that can receive events
- * and may have listeners for them.
- */
-declare class EventTarget {
-  /** Appends an event listener for events whose type attribute value is type.
-   * The callback argument sets the callback that will be invoked when the event
-   * is dispatched.
-   *
-   * The options argument sets listener-specific options. For compatibility this
-   * can be a boolean, in which case the method behaves exactly as if the value
-   * was specified as options's capture.
-   *
-   * When set to true, options's capture prevents callback from being invoked
-   * when the event's eventPhase attribute value is BUBBLING_PHASE. When false
-   * (or not present), callback will not be invoked when event's eventPhase
-   * attribute value is CAPTURING_PHASE. Either way, callback will be invoked if
-   * event's eventPhase attribute value is AT_TARGET.
-   *
-   * When set to true, options's passive indicates that the callback will not
-   * cancel the event by invoking preventDefault(). This is used to enable
-   * performance optimizations described in § 2.8 Observing event listeners.
-   *
-   * When set to true, options's once indicates that the callback will only be
-   * invoked once after which the event listener will be removed.
-   *
-   * The event listener is appended to target's event listener list and is not
-   * appended if it has the same type, callback, and capture. */
-  addEventListener(
-    type: string,
-    listener: EventListenerOrEventListenerObject | null,
-    options?: boolean | AddEventListenerOptions,
-  ): void;
-  /** Dispatches a synthetic event event to target and returns true if either
-   * event's cancelable attribute value is false or its preventDefault() method
-   * was not invoked, and false otherwise. */
-  dispatchEvent(event: Event): boolean;
-  /** Removes the event listener in target's event listener list with the same
-   * type, callback, and options. */
-  removeEventListener(
-    type: string,
-    callback: EventListenerOrEventListenerObject | null,
-    options?: EventListenerOptions | boolean,
-  ): void;
-  [Symbol.toStringTag]: string;
-}
-
-interface EventListener {
-  (evt: Event): void | Promise<void>;
-}
-
-interface EventListenerObject {
-  handleEvent(evt: Event): void | Promise<void>;
-}
-
-declare type EventListenerOrEventListenerObject =
-  | EventListener
-  | EventListenerObject;
-
-interface AddEventListenerOptions extends EventListenerOptions {
-  once?: boolean;
-  passive?: boolean;
-}
-
-interface EventListenerOptions {
-  capture?: boolean;
-}
-
 /** Events measuring progress of an underlying process, like an HTTP request
  * (for an XMLHttpRequest, or the loading of the underlying resource of an
  * <img>, <audio>, <video>, <style> or <link>). */
diff --git a/cli/js.rs b/cli/js.rs
index f04f1ee91..763b62aed 100644
--- a/cli/js.rs
+++ b/cli/js.rs
@@ -5,6 +5,7 @@ pub static CLI_SNAPSHOT: &[u8] =
 pub static COMPILER_SNAPSHOT: &[u8] =
   include_bytes!(concat!(env!("OUT_DIR"), "/COMPILER_SNAPSHOT.bin"));
 pub static DENO_NS_LIB: &str = include_str!("dts/lib.deno.ns.d.ts");
+pub static DENO_WEB_LIB: &str = include_str!(env!("DENO_WEB_LIB_PATH"));
 pub static SHARED_GLOBALS_LIB: &str =
   include_str!("dts/lib.deno.shared_globals.d.ts");
 pub static WINDOW_LIB: &str = include_str!("dts/lib.deno.window.d.ts");
diff --git a/cli/main.rs b/cli/main.rs
index 97f3161df..728a23db0 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -287,8 +287,9 @@ async fn print_file_info(
 
 fn get_types(unstable: bool) -> String {
   let mut types = format!(
-    "{}\n{}\n{}",
+    "{}\n{}\n{}\n{}",
     crate::js::DENO_NS_LIB,
+    crate::js::DENO_WEB_LIB,
     crate::js::SHARED_GLOBALS_LIB,
     crate::js::WINDOW_LIB,
   );
diff --git a/cli/rt/07_base64.js b/cli/rt/07_base64.js
deleted file mode 100644
index 86739fd52..000000000
--- a/cli/rt/07_base64.js
+++ /dev/null
@@ -1,157 +0,0 @@
-// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-
-// Forked from https://github.com/beatgammit/base64-js
-// Copyright (c) 2014 Jameson Little. MIT License.
-
-((window) => {
-  const lookup = [];
-  const revLookup = [];
-
-  const code =
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-  for (let i = 0, len = code.length; i < len; ++i) {
-    lookup[i] = code[i];
-    revLookup[code.charCodeAt(i)] = i;
-  }
-
-  // Support decoding URL-safe base64 strings, as Node.js does.
-  // See: https://en.wikipedia.org/wiki/Base64#URL_applications
-  revLookup["-".charCodeAt(0)] = 62;
-  revLookup["_".charCodeAt(0)] = 63;
-
-  function getLens(b64) {
-    const len = b64.length;
-
-    if (len % 4 > 0) {
-      throw new Error("Invalid string. Length must be a multiple of 4");
-    }
-
-    // Trim off extra bytes after placeholder bytes are found
-    // See: https://github.com/beatgammit/base64-js/issues/42
-    let validLen = b64.indexOf("=");
-    if (validLen === -1) validLen = len;
-
-    const placeHoldersLen = validLen === len ? 0 : 4 - (validLen % 4);
-
-    return [validLen, placeHoldersLen];
-  }
-
-  // base64 is 4/3 + up to two characters of the original data
-  function byteLength(b64) {
-    const lens = getLens(b64);
-    const validLen = lens[0];
-    const placeHoldersLen = lens[1];
-    return ((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;
-  }
-
-  function _byteLength(
-    b64,
-    validLen,
-    placeHoldersLen,
-  ) {
-    return ((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;
-  }
-
-  function toByteArray(b64) {
-    let tmp;
-    const lens = getLens(b64);
-    const validLen = lens[0];
-    const placeHoldersLen = lens[1];
-
-    const arr = new Uint8Array(_byteLength(b64, validLen, placeHoldersLen));
-
-    let curByte = 0;
-
-    // if there are placeholders, only get up to the last complete 4 chars
-    const len = placeHoldersLen > 0 ? validLen - 4 : validLen;
-
-    let i;
-    for (i = 0; i < len; i += 4) {
-      tmp = (revLookup[b64.charCodeAt(i)] << 18) |
-        (revLookup[b64.charCodeAt(i + 1)] << 12) |
-        (revLookup[b64.charCodeAt(i + 2)] << 6) |
-        revLookup[b64.charCodeAt(i + 3)];
-      arr[curByte++] = (tmp >> 16) & 0xff;
-      arr[curByte++] = (tmp >> 8) & 0xff;
-      arr[curByte++] = tmp & 0xff;
-    }
-
-    if (placeHoldersLen === 2) {
-      tmp = (revLookup[b64.charCodeAt(i)] << 2) |
-        (revLookup[b64.charCodeAt(i + 1)] >> 4);
-      arr[curByte++] = tmp & 0xff;
-    }
-
-    if (placeHoldersLen === 1) {
-      tmp = (revLookup[b64.charCodeAt(i)] << 10) |
-        (revLookup[b64.charCodeAt(i + 1)] << 4) |
-        (revLookup[b64.charCodeAt(i + 2)] >> 2);
-      arr[curByte++] = (tmp >> 8) & 0xff;
-      arr[curByte++] = tmp & 0xff;
-    }
-
-    return arr;
-  }
-
-  function tripletToBase64(num) {
-    return (
-      lookup[(num >> 18) & 0x3f] +
-      lookup[(num >> 12) & 0x3f] +
-      lookup[(num >> 6) & 0x3f] +
-      lookup[num & 0x3f]
-    );
-  }
-
-  function encodeChunk(uint8, start, end) {
-    let tmp;
-    const output = [];
-    for (let i = start; i < end; i += 3) {
-      tmp = ((uint8[i] << 16) & 0xff0000) +
-        ((uint8[i + 1] << 8) & 0xff00) +
-        (uint8[i + 2] & 0xff);
-      output.push(tripletToBase64(tmp));
-    }
-    return output.join("");
-  }
-
-  function fromByteArray(uint8) {
-    let tmp;
-    const len = uint8.length;
-    const extraBytes = len % 3; // if we have 1 byte left, pad 2 bytes
-    const parts = [];
-    const maxChunkLength = 16383; // must be multiple of 3
-
-    // go through the array every three bytes, we'll deal with trailing stuff later
-    for (let i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
-      parts.push(
-        encodeChunk(
-          uint8,
-          i,
-          i + maxChunkLength > len2 ? len2 : i + maxChunkLength,
-        ),
-      );
-    }
-
-    // pad the end with zeros, but make sure to not forget the extra bytes
-    if (extraBytes === 1) {
-      tmp = uint8[len - 1];
-      parts.push(lookup[tmp >> 2] + lookup[(tmp << 4) & 0x3f] + "==");
-    } else if (extraBytes === 2) {
-      tmp = (uint8[len - 2] << 8) + uint8[len - 1];
-      parts.push(
-        lookup[tmp >> 10] +
-          lookup[(tmp >> 4) & 0x3f] +
-          lookup[(tmp << 2) & 0x3f] +
-          "=",
-      );
-    }
-
-    return parts.join("");
-  }
-
-  window.__bootstrap.base64 = {
-    byteLength,
-    toByteArray,
-    fromByteArray,
-  };
-})(this);
diff --git a/cli/tests/performance_stats.out b/cli/tests/performance_stats.out
index 9fea7715a..c623d81da 100644
--- a/cli/tests/performance_stats.out
+++ b/cli/tests/performance_stats.out
@@ -1,5 +1,5 @@
 [WILDCARD]
-Files: 43
+Files: 44
 Nodes: [WILDCARD]
 Identifiers: [WILDCARD]
 Symbols: [WILDCARD]
diff --git a/cli/tsc/99_main_compiler.js b/cli/tsc/99_main_compiler.js
index b8673b790..41051f2e0 100644
--- a/cli/tsc/99_main_compiler.js
+++ b/cli/tsc/99_main_compiler.js
@@ -776,6 +776,7 @@ delete Object.prototype.__proto__;
   // as these are internal APIs of TypeScript which maintain valid libs
   ts.libs.push("deno.ns", "deno.window", "deno.worker", "deno.shared_globals");
   ts.libMap.set("deno.ns", "lib.deno.ns.d.ts");
+  ts.libMap.set("deno.web", "lib.deno.web.d.ts");
   ts.libMap.set("deno.window", "lib.deno.window.d.ts");
   ts.libMap.set("deno.worker", "lib.deno.worker.d.ts");
   ts.libMap.set("deno.shared_globals", "lib.deno.shared_globals.d.ts");
@@ -788,6 +789,10 @@ delete Object.prototype.__proto__;
     ts.ScriptTarget.ESNext,
   );
   SNAPSHOT_HOST.getSourceFile(
+    `${ASSETS}/lib.deno.web.d.ts`,
+    ts.ScriptTarget.ESNext,
+  );
+  SNAPSHOT_HOST.getSourceFile(
     `${ASSETS}/lib.deno.window.d.ts`,
     ts.ScriptTarget.ESNext,
   );
diff --git a/cli/rt/00_dom_exception.js b/op_crates/web/00_dom_exception.js
index 6d72779b0..6d72779b0 100644
--- a/cli/rt/00_dom_exception.js
+++ b/op_crates/web/00_dom_exception.js
diff --git a/cli/rt/01_event.js b/op_crates/web/01_event.js
index 35967e0a1..48899e6fd 100644
--- a/cli/rt/01_event.js
+++ b/op_crates/web/01_event.js
@@ -1038,6 +1038,10 @@
   window.EventTarget = EventTarget;
   window.ErrorEvent = ErrorEvent;
   window.CustomEvent = CustomEvent;
+  window.dispatchEvent = EventTarget.prototype.dispatchEvent;
+  window.addEventListener = EventTarget.prototype.addEventListener;
+  window.removeEventListener = EventTarget.prototype.removeEventListener;
+  window.__bootstrap = (window.__bootstrap || {});
   window.__bootstrap.eventTarget = {
     setEventTargetData,
   };
diff --git a/cli/rt/08_text_encoding.js b/op_crates/web/08_text_encoding.js
index a7a9a49e4..b8959142f 100644
--- a/cli/rt/08_text_encoding.js
+++ b/op_crates/web/08_text_encoding.js
@@ -26,7 +26,6 @@
 
 ((window) => {
   const core = Deno.core;
-  const base64 = window.__bootstrap.base64;
 
   const CONTINUE = null;
   const END_OF_STREAM = -1;
@@ -679,6 +678,159 @@
     return outString;
   }
 
+  // Following code is forked from https://github.com/beatgammit/base64-js
+  // Copyright (c) 2014 Jameson Little. MIT License.
+  const lookup = [];
+  const revLookup = [];
+
+  const code =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+  for (let i = 0, len = code.length; i < len; ++i) {
+    lookup[i] = code[i];
+    revLookup[code.charCodeAt(i)] = i;
+  }
+
+  // Support decoding URL-safe base64 strings, as Node.js does.
+  // See: https://en.wikipedia.org/wiki/Base64#URL_applications
+  revLookup["-".charCodeAt(0)] = 62;
+  revLookup["_".charCodeAt(0)] = 63;
+
+  function getLens(b64) {
+    const len = b64.length;
+
+    if (len % 4 > 0) {
+      throw new Error("Invalid string. Length must be a multiple of 4");
+    }
+
+    // Trim off extra bytes after placeholder bytes are found
+    // See: https://github.com/beatgammit/base64-js/issues/42
+    let validLen = b64.indexOf("=");
+    if (validLen === -1) validLen = len;
+
+    const placeHoldersLen = validLen === len ? 0 : 4 - (validLen % 4);
+
+    return [validLen, placeHoldersLen];
+  }
+
+  // base64 is 4/3 + up to two characters of the original data
+  function byteLength(b64) {
+    const lens = getLens(b64);
+    const validLen = lens[0];
+    const placeHoldersLen = lens[1];
+    return ((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;
+  }
+
+  function _byteLength(
+    b64,
+    validLen,
+    placeHoldersLen,
+  ) {
+    return ((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;
+  }
+
+  function toByteArray(b64) {
+    let tmp;
+    const lens = getLens(b64);
+    const validLen = lens[0];
+    const placeHoldersLen = lens[1];
+
+    const arr = new Uint8Array(_byteLength(b64, validLen, placeHoldersLen));
+
+    let curByte = 0;
+
+    // if there are placeholders, only get up to the last complete 4 chars
+    const len = placeHoldersLen > 0 ? validLen - 4 : validLen;
+
+    let i;
+    for (i = 0; i < len; i += 4) {
+      tmp = (revLookup[b64.charCodeAt(i)] << 18) |
+        (revLookup[b64.charCodeAt(i + 1)] << 12) |
+        (revLookup[b64.charCodeAt(i + 2)] << 6) |
+        revLookup[b64.charCodeAt(i + 3)];
+      arr[curByte++] = (tmp >> 16) & 0xff;
+      arr[curByte++] = (tmp >> 8) & 0xff;
+      arr[curByte++] = tmp & 0xff;
+    }
+
+    if (placeHoldersLen === 2) {
+      tmp = (revLookup[b64.charCodeAt(i)] << 2) |
+        (revLookup[b64.charCodeAt(i + 1)] >> 4);
+      arr[curByte++] = tmp & 0xff;
+    }
+
+    if (placeHoldersLen === 1) {
+      tmp = (revLookup[b64.charCodeAt(i)] << 10) |
+        (revLookup[b64.charCodeAt(i + 1)] << 4) |
+        (revLookup[b64.charCodeAt(i + 2)] >> 2);
+      arr[curByte++] = (tmp >> 8) & 0xff;
+      arr[curByte++] = tmp & 0xff;
+    }
+
+    return arr;
+  }
+
+  function tripletToBase64(num) {
+    return (
+      lookup[(num >> 18) & 0x3f] +
+      lookup[(num >> 12) & 0x3f] +
+      lookup[(num >> 6) & 0x3f] +
+      lookup[num & 0x3f]
+    );
+  }
+
+  function encodeChunk(uint8, start, end) {
+    let tmp;
+    const output = [];
+    for (let i = start; i < end; i += 3) {
+      tmp = ((uint8[i] << 16) & 0xff0000) +
+        ((uint8[i + 1] << 8) & 0xff00) +
+        (uint8[i + 2] & 0xff);
+      output.push(tripletToBase64(tmp));
+    }
+    return output.join("");
+  }
+
+  function fromByteArray(uint8) {
+    let tmp;
+    const len = uint8.length;
+    const extraBytes = len % 3; // if we have 1 byte left, pad 2 bytes
+    const parts = [];
+    const maxChunkLength = 16383; // must be multiple of 3
+
+    // go through the array every three bytes, we'll deal with trailing stuff later
+    for (let i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
+      parts.push(
+        encodeChunk(
+          uint8,
+          i,
+          i + maxChunkLength > len2 ? len2 : i + maxChunkLength,
+        ),
+      );
+    }
+
+    // pad the end with zeros, but make sure to not forget the extra bytes
+    if (extraBytes === 1) {
+      tmp = uint8[len - 1];
+      parts.push(lookup[tmp >> 2] + lookup[(tmp << 4) & 0x3f] + "==");
+    } else if (extraBytes === 2) {
+      tmp = (uint8[len - 2] << 8) + uint8[len - 1];
+      parts.push(
+        lookup[tmp >> 10] +
+          lookup[(tmp >> 4) & 0x3f] +
+          lookup[(tmp << 2) & 0x3f] +
+          "=",
+      );
+    }
+
+    return parts.join("");
+  }
+
+  const base64 = {
+    byteLength,
+    toByteArray,
+    fromByteArray,
+  };
+
   window.TextEncoder = TextEncoder;
   window.TextDecoder = TextDecoder;
   window.atob = atob;
diff --git a/op_crates/web/Cargo.toml b/op_crates/web/Cargo.toml
new file mode 100644
index 000000000..ae5677561
--- /dev/null
+++ b/op_crates/web/Cargo.toml
@@ -0,0 +1,20 @@
+# Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+[package]
+name = "deno_web"
+version = "0.1.0"
+edition = "2018"
+description = "Collection of Web APIs"
+authors = ["the Deno authors"]
+license = "MIT"
+readme = "README.md"
+repository = "https://github.com/denoland/deno"
+
+[lib]
+path = "lib.rs"
+
+[dependencies]
+deno_core = { version = "0.51.0", path = "../../core" }
+
+[dev-dependencies]
+futures = "0.3.5"
diff --git a/op_crates/web/event_target_test.js b/op_crates/web/event_target_test.js
new file mode 100644
index 000000000..5e86c6efb
--- /dev/null
+++ b/op_crates/web/event_target_test.js
@@ -0,0 +1,244 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+function assert(cond) {
+  if (!cond) {
+    throw Error("assert");
+  }
+}
+
+function addEventListenerTest() {
+  const document = new EventTarget();
+
+  assert(document.addEventListener("x", null, false) === undefined);
+  assert(document.addEventListener("x", null, true) === undefined);
+  assert(document.addEventListener("x", null) === undefined);
+}
+
+function constructedEventTargetCanBeUsedAsExpected() {
+  const target = new EventTarget();
+  const event = new Event("foo", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  const listener = (e) => {
+    assert(e === event);
+    ++callCount;
+  };
+
+  target.addEventListener("foo", listener);
+
+  target.dispatchEvent(event);
+  assert(callCount === 1);
+
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+
+  target.removeEventListener("foo", listener);
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+}
+
+function anEventTargetCanBeSubclassed() {
+  class NicerEventTarget extends EventTarget {
+    on(
+      type,
+      callback,
+      options,
+    ) {
+      this.addEventListener(type, callback, options);
+    }
+
+    off(
+      type,
+      callback,
+      options,
+    ) {
+      this.removeEventListener(type, callback, options);
+    }
+  }
+
+  const target = new NicerEventTarget();
+  new Event("foo", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  const listener = () => {
+    ++callCount;
+  };
+
+  target.on("foo", listener);
+  assert(callCount === 0);
+
+  target.off("foo", listener);
+  assert(callCount === 0);
+}
+
+function removingNullEventListenerShouldSucceed() {
+  const document = new EventTarget();
+  assert(document.removeEventListener("x", null, false) === undefined);
+  assert(document.removeEventListener("x", null, true) === undefined);
+  assert(document.removeEventListener("x", null) === undefined);
+}
+
+function constructedEventTargetUseObjectPrototype() {
+  const target = new EventTarget();
+  const event = new Event("toString", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  const listener = (e) => {
+    assert(e === event);
+    ++callCount;
+  };
+
+  target.addEventListener("toString", listener);
+
+  target.dispatchEvent(event);
+  assert(callCount === 1);
+
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+
+  target.removeEventListener("toString", listener);
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+}
+
+function toStringShouldBeWebCompatible() {
+  const target = new EventTarget();
+  assert(target.toString() === "[object EventTarget]");
+}
+
+function dispatchEventShouldNotThrowError() {
+  let hasThrown = false;
+
+  try {
+    const target = new EventTarget();
+    const event = new Event("hasOwnProperty", {
+      bubbles: true,
+      cancelable: false,
+    });
+    const listener = () => {};
+    target.addEventListener("hasOwnProperty", listener);
+    target.dispatchEvent(event);
+  } catch {
+    hasThrown = true;
+  }
+
+  assert(hasThrown === false);
+}
+
+function eventTargetThisShouldDefaultToWindow() {
+  const {
+    addEventListener,
+    dispatchEvent,
+    removeEventListener,
+  } = EventTarget.prototype;
+  let n = 1;
+  const event = new Event("hello");
+  const listener = () => {
+    n = 2;
+  };
+
+  addEventListener("hello", listener);
+  globalThis.dispatchEvent(event);
+  assert(n === 2);
+  n = 1;
+  removeEventListener("hello", listener);
+  globalThis.dispatchEvent(event);
+  assert(n === 1);
+
+  globalThis.addEventListener("hello", listener);
+  dispatchEvent(event);
+  assert(n === 2);
+  n = 1;
+  globalThis.removeEventListener("hello", listener);
+  dispatchEvent(event);
+  assert(n === 1);
+}
+
+function eventTargetShouldAcceptEventListenerObject() {
+  const target = new EventTarget();
+  const event = new Event("foo", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  const listener = {
+    handleEvent(e) {
+      assert(e === event);
+      ++callCount;
+    },
+  };
+
+  target.addEventListener("foo", listener);
+
+  target.dispatchEvent(event);
+  assert(callCount === 1);
+
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+
+  target.removeEventListener("foo", listener);
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+}
+
+function eventTargetShouldAcceptAsyncFunction() {
+  const target = new EventTarget();
+  const event = new Event("foo", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  const listener = (e) => {
+    assert(e === event);
+    ++callCount;
+  };
+
+  target.addEventListener("foo", listener);
+
+  target.dispatchEvent(event);
+  assert(callCount === 1);
+
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+
+  target.removeEventListener("foo", listener);
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+}
+
+function eventTargetShouldAcceptAsyncFunctionForEventListenerObject() {
+  const target = new EventTarget();
+  const event = new Event("foo", { bubbles: true, cancelable: false });
+  let callCount = 0;
+
+  const listener = {
+    handleEvent(e) {
+      assert(e === event);
+      ++callCount;
+    },
+  };
+
+  target.addEventListener("foo", listener);
+
+  target.dispatchEvent(event);
+  assert(callCount === 1);
+
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+
+  target.removeEventListener("foo", listener);
+  target.dispatchEvent(event);
+  assert(callCount === 2);
+}
+
+function main() {
+  globalThis.__bootstrap.eventTarget.setEventTargetData(globalThis);
+  addEventListenerTest();
+  constructedEventTargetCanBeUsedAsExpected();
+  anEventTargetCanBeSubclassed();
+  removingNullEventListenerShouldSucceed();
+  constructedEventTargetUseObjectPrototype();
+  toStringShouldBeWebCompatible();
+  dispatchEventShouldNotThrowError();
+  eventTargetThisShouldDefaultToWindow();
+  eventTargetShouldAcceptEventListenerObject();
+  eventTargetShouldAcceptAsyncFunction();
+  eventTargetShouldAcceptAsyncFunctionForEventListenerObject();
+}
+
+main();
diff --git a/op_crates/web/event_test.js b/op_crates/web/event_test.js
new file mode 100644
index 000000000..4f9f94fa9
--- /dev/null
+++ b/op_crates/web/event_test.js
@@ -0,0 +1,111 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+function assert(cond) {
+  if (!cond) {
+    throw Error("assert");
+  }
+}
+
+function eventInitializedWithType() {
+  const type = "click";
+  const event = new Event(type);
+
+  assert(event.isTrusted === false);
+  assert(event.target === null);
+  assert(event.currentTarget === null);
+  assert(event.type === "click");
+  assert(event.bubbles === false);
+  assert(event.cancelable === false);
+}
+
+function eventInitializedWithTypeAndDict() {
+  const init = "submit";
+  const eventInit = { bubbles: true, cancelable: true };
+  const event = new Event(init, eventInit);
+
+  assert(event.isTrusted === false);
+  assert(event.target === null);
+  assert(event.currentTarget === null);
+  assert(event.type === "submit");
+  assert(event.bubbles === true);
+  assert(event.cancelable === true);
+}
+
+function eventComposedPathSuccess() {
+  const type = "click";
+  const event = new Event(type);
+  const composedPath = event.composedPath();
+
+  assert(composedPath.length === 0);
+}
+
+function eventStopPropagationSuccess() {
+  const type = "click";
+  const event = new Event(type);
+
+  assert(event.cancelBubble === false);
+  event.stopPropagation();
+  assert(event.cancelBubble === true);
+}
+
+function eventStopImmediatePropagationSuccess() {
+  const type = "click";
+  const event = new Event(type);
+
+  assert(event.cancelBubble === false);
+  event.stopImmediatePropagation();
+  assert(event.cancelBubble === true);
+}
+
+function eventPreventDefaultSuccess() {
+  const type = "click";
+  const event = new Event(type);
+
+  assert(event.defaultPrevented === false);
+  event.preventDefault();
+  assert(event.defaultPrevented === false);
+
+  const eventInit = { bubbles: true, cancelable: true };
+  const cancelableEvent = new Event(type, eventInit);
+  assert(cancelableEvent.defaultPrevented === false);
+  cancelableEvent.preventDefault();
+  assert(cancelableEvent.defaultPrevented === true);
+}
+
+function eventInitializedWithNonStringType() {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  const type = undefined;
+  const event = new Event(type);
+
+  assert(event.isTrusted === false);
+  assert(event.target === null);
+  assert(event.currentTarget === null);
+  assert(event.type === "undefined");
+  assert(event.bubbles === false);
+  assert(event.cancelable === false);
+}
+
+// ref https://github.com/web-platform-tests/wpt/blob/master/dom/events/Event-isTrusted.any.js
+function eventIsTrusted() {
+  const desc1 = Object.getOwnPropertyDescriptor(new Event("x"), "isTrusted");
+  assert(desc1);
+  assert(typeof desc1.get === "function");
+
+  const desc2 = Object.getOwnPropertyDescriptor(new Event("x"), "isTrusted");
+  assert(desc2);
+  assert(typeof desc2.get === "function");
+
+  assert(desc1.get === desc2.get);
+}
+
+function main() {
+  eventInitializedWithType();
+  eventInitializedWithTypeAndDict();
+  eventComposedPathSuccess();
+  eventStopPropagationSuccess();
+  eventStopImmediatePropagationSuccess();
+  eventPreventDefaultSuccess();
+  eventInitializedWithNonStringType();
+  eventIsTrusted();
+}
+
+main();
diff --git a/op_crates/web/lib.deno_web.d.ts b/op_crates/web/lib.deno_web.d.ts
new file mode 100644
index 000000000..b402529e2
--- /dev/null
+++ b/op_crates/web/lib.deno_web.d.ts
@@ -0,0 +1,187 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+/// <reference no-default-lib="true" />
+/// <reference lib="esnext" />
+
+declare class DOMException extends Error {
+  constructor(message?: string, name?: string);
+  readonly name: string;
+  readonly message: string;
+}
+
+interface EventInit {
+  bubbles?: boolean;
+  cancelable?: boolean;
+  composed?: boolean;
+}
+
+/** An event which takes place in the DOM. */
+declare class Event {
+  constructor(type: string, eventInitDict?: EventInit);
+  /** Returns true or false depending on how event was initialized. True if
+     * event goes through its target's ancestors in reverse tree order, and
+     * false otherwise. */
+  readonly bubbles: boolean;
+  cancelBubble: boolean;
+  /** Returns true or false depending on how event was initialized. Its return
+     * value does not always carry meaning, but true can indicate that part of the
+     * operation during which event was dispatched, can be canceled by invoking
+     * the preventDefault() method. */
+  readonly cancelable: boolean;
+  /** Returns true or false depending on how event was initialized. True if
+     * event invokes listeners past a ShadowRoot node that is the root of its
+     * target, and false otherwise. */
+  readonly composed: boolean;
+  /** Returns the object whose event listener's callback is currently being
+     * invoked. */
+  readonly currentTarget: EventTarget | null;
+  /** Returns true if preventDefault() was invoked successfully to indicate
+     * cancellation, and false otherwise. */
+  readonly defaultPrevented: boolean;
+  /** Returns the event's phase, which is one of NONE, CAPTURING_PHASE,
+     * AT_TARGET, and BUBBLING_PHASE. */
+  readonly eventPhase: number;
+  /** Returns true if event was dispatched by the user agent, and false
+     * otherwise. */
+  readonly isTrusted: boolean;
+  /** Returns the object to which event is dispatched (its target). */
+  readonly target: EventTarget | null;
+  /** Returns the event's timestamp as the number of milliseconds measured
+     * relative to the time origin. */
+  readonly timeStamp: number;
+  /** Returns the type of event, e.g. "click", "hashchange", or "submit". */
+  readonly type: string;
+  /** Returns the invocation target objects of event's path (objects on which
+     * listeners will be invoked), except for any nodes in shadow trees of which
+     * the shadow root's mode is "closed" that are not reachable from event's
+     * currentTarget. */
+  composedPath(): EventTarget[];
+  /** If invoked when the cancelable attribute value is true, and while
+     * executing a listener for the event with passive set to false, signals to
+     * the operation that caused event to be dispatched that it needs to be
+     * canceled. */
+  preventDefault(): void;
+  /** Invoking this method prevents event from reaching any registered event
+     * listeners after the current one finishes running and, when dispatched in a
+     * tree, also prevents event from reaching any other objects. */
+  stopImmediatePropagation(): void;
+  /** When dispatched in a tree, invoking this method prevents event from
+     * reaching any objects other than the current object. */
+  stopPropagation(): void;
+  readonly AT_TARGET: number;
+  readonly BUBBLING_PHASE: number;
+  readonly CAPTURING_PHASE: number;
+  readonly NONE: number;
+  static readonly AT_TARGET: number;
+  static readonly BUBBLING_PHASE: number;
+  static readonly CAPTURING_PHASE: number;
+  static readonly NONE: number;
+}
+
+/**
+   * EventTarget is a DOM interface implemented by objects that can receive events
+   * and may have listeners for them.
+   */
+declare class EventTarget {
+  /** Appends an event listener for events whose type attribute value is type.
+     * The callback argument sets the callback that will be invoked when the event
+     * is dispatched.
+     *
+     * The options argument sets listener-specific options. For compatibility this
+     * can be a boolean, in which case the method behaves exactly as if the value
+     * was specified as options's capture.
+     *
+     * When set to true, options's capture prevents callback from being invoked
+     * when the event's eventPhase attribute value is BUBBLING_PHASE. When false
+     * (or not present), callback will not be invoked when event's eventPhase
+     * attribute value is CAPTURING_PHASE. Either way, callback will be invoked if
+     * event's eventPhase attribute value is AT_TARGET.
+     *
+     * When set to true, options's passive indicates that the callback will not
+     * cancel the event by invoking preventDefault(). This is used to enable
+     * performance optimizations described in § 2.8 Observing event listeners.
+     *
+     * When set to true, options's once indicates that the callback will only be
+     * invoked once after which the event listener will be removed.
+     *
+     * The event listener is appended to target's event listener list and is not
+     * appended if it has the same type, callback, and capture. */
+  addEventListener(
+    type: string,
+    listener: EventListenerOrEventListenerObject | null,
+    options?: boolean | AddEventListenerOptions,
+  ): void;
+  /** Dispatches a synthetic event event to target and returns true if either
+     * event's cancelable attribute value is false or its preventDefault() method
+     * was not invoked, and false otherwise. */
+  dispatchEvent(event: Event): boolean;
+  /** Removes the event listener in target's event listener list with the same
+     * type, callback, and options. */
+  removeEventListener(
+    type: string,
+    callback: EventListenerOrEventListenerObject | null,
+    options?: EventListenerOptions | boolean,
+  ): void;
+  [Symbol.toStringTag]: string;
+}
+
+interface EventListener {
+  (evt: Event): void | Promise<void>;
+}
+
+interface EventListenerObject {
+  handleEvent(evt: Event): void | Promise<void>;
+}
+
+declare type EventListenerOrEventListenerObject =
+  | EventListener
+  | EventListenerObject;
+
+interface AddEventListenerOptions extends EventListenerOptions {
+  once?: boolean;
+  passive?: boolean;
+}
+
+interface EventListenerOptions {
+  capture?: boolean;
+}
+
+/** Decodes a string of data which has been encoded using base-64 encoding.
+ *
+ *     console.log(atob("aGVsbG8gd29ybGQ=")); // outputs 'hello world'
+ */
+declare function atob(s: string): string;
+
+/** Creates a base-64 ASCII encoded string from the input string.
+ *
+ *     console.log(btoa("hello world"));  // outputs "aGVsbG8gd29ybGQ="
+ */
+declare function btoa(s: string): string;
+
+declare class TextDecoder {
+  /** Returns encoding's name, lowercased. */
+  readonly encoding: string;
+  /** Returns `true` if error mode is "fatal", and `false` otherwise. */
+  readonly fatal: boolean;
+  /** Returns `true` if ignore BOM flag is set, and `false` otherwise. */
+  readonly ignoreBOM = false;
+  constructor(
+    label?: string,
+    options?: { fatal?: boolean; ignoreBOM?: boolean },
+  );
+  /** Returns the result of running encoding's decoder. */
+  decode(input?: BufferSource, options?: { stream?: false }): string;
+  readonly [Symbol.toStringTag]: string;
+}
+
+declare class TextEncoder {
+  /** Returns "utf-8". */
+  readonly encoding = "utf-8";
+  /** Returns the result of running UTF-8's encoder. */
+  encode(input?: string): Uint8Array;
+  encodeInto(
+    input: string,
+    dest: Uint8Array,
+  ): { read: number; written: number };
+  readonly [Symbol.toStringTag]: string;
+}
diff --git a/op_crates/web/lib.rs b/op_crates/web/lib.rs
new file mode 100644
index 000000000..4cfe8d090
--- /dev/null
+++ b/op_crates/web/lib.rs
@@ -0,0 +1,102 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+use deno_core::crate_modules;
+use std::path::PathBuf;
+
+crate_modules!();
+
+pub struct WebScripts {
+  pub declaration: String,
+  pub dom_exception: String,
+  pub event: String,
+  pub text_encoding: String,
+}
+
+fn get_str_path(file_name: &str) -> String {
+  PathBuf::from(DENO_CRATE_PATH)
+    .join(file_name)
+    .to_string_lossy()
+    .to_string()
+}
+
+pub fn get_scripts() -> WebScripts {
+  WebScripts {
+    declaration: get_str_path("lib.deno_web.d.ts"),
+    dom_exception: get_str_path("00_dom_exception.js"),
+    event: get_str_path("01_event.js"),
+    text_encoding: get_str_path("08_text_encoding.js"),
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use deno_core::js_check;
+  use deno_core::CoreIsolate;
+  use deno_core::StartupData;
+  use futures::future::lazy;
+  use futures::future::FutureExt;
+  use futures::task::Context;
+  use futures::task::Poll;
+
+  fn run_in_task<F>(f: F)
+  where
+    F: FnOnce(&mut Context) + Send + 'static,
+  {
+    futures::executor::block_on(lazy(move |cx| f(cx)));
+  }
+
+  fn setup() -> CoreIsolate {
+    let mut isolate = CoreIsolate::new(StartupData::None, false);
+    js_check(
+      isolate
+        .execute("00_dom_exception.js", include_str!("00_dom_exception.js")),
+    );
+    js_check(isolate.execute("01_event.js", include_str!("01_event.js")));
+    js_check(
+      isolate
+        .execute("08_text_encoding.js", include_str!("08_text_encoding.js")),
+    );
+    isolate
+  }
+
+  #[test]
+  fn test_event() {
+    run_in_task(|mut cx| {
+      let mut isolate = setup();
+      js_check(isolate.execute("event_test.js", include_str!("event_test.js")));
+      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+        unreachable!();
+      }
+    });
+  }
+
+  #[test]
+  fn test_event_target() {
+    run_in_task(|mut cx| {
+      let mut isolate = setup();
+      js_check(
+        isolate.execute(
+          "event_target_test.js",
+          include_str!("event_target_test.js"),
+        ),
+      );
+      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+        unreachable!();
+      }
+    });
+  }
+
+  #[test]
+  fn test_text_encoding() {
+    run_in_task(|mut cx| {
+      let mut isolate = setup();
+      js_check(isolate.execute(
+        "text_encoding_test.js",
+        include_str!("text_encoding_test.js"),
+      ));
+      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+        unreachable!();
+      }
+    });
+  }
+}
diff --git a/op_crates/web/text_encoding_test.js b/op_crates/web/text_encoding_test.js
new file mode 100644
index 000000000..f741fe409
--- /dev/null
+++ b/op_crates/web/text_encoding_test.js
@@ -0,0 +1,243 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+function assert(cond) {
+  if (!cond) {
+    throw Error("assert");
+  }
+}
+
+function assertArrayEquals(a1, a2) {
+  if (a1.length !== a2.length) throw Error("assert");
+
+  for (const index in a1) {
+    if (a1[index] !== a2[index]) {
+      throw Error("assert");
+    }
+  }
+}
+
+function btoaSuccess() {
+  const text = "hello world";
+  const encoded = btoa(text);
+  assert(encoded === "aGVsbG8gd29ybGQ=");
+}
+
+function atobSuccess() {
+  const encoded = "aGVsbG8gd29ybGQ=";
+  const decoded = atob(encoded);
+  assert(decoded === "hello world");
+}
+
+function atobWithAsciiWhitespace() {
+  const encodedList = [
+    " aGVsbG8gd29ybGQ=",
+    "  aGVsbG8gd29ybGQ=",
+    "aGVsbG8gd29ybGQ= ",
+    "aGVsbG8gd29ybGQ=\n",
+    "aGVsbG\t8gd29ybGQ=",
+    `aGVsbG\t8g
+                d29ybGQ=`,
+  ];
+
+  for (const encoded of encodedList) {
+    const decoded = atob(encoded);
+    assert(decoded === "hello world");
+  }
+}
+
+function atobThrows() {
+  let threw = false;
+  try {
+    atob("aGVsbG8gd29ybGQ==");
+  } catch (e) {
+    threw = true;
+  }
+  assert(threw);
+}
+
+function atobThrows2() {
+  let threw = false;
+  try {
+    atob("aGVsbG8gd29ybGQ===");
+  } catch (e) {
+    threw = true;
+  }
+  assert(threw);
+}
+
+function btoaFailed() {
+  let threw = false;
+  const text = "你好";
+  try {
+    btoa(text);
+  } catch (e) {
+    assert(e instanceof TypeError);
+    threw = true;
+  }
+  assert(threw);
+}
+
+function textDecoder2() {
+  // deno-fmt-ignore
+  const fixture = new Uint8Array([
+    0xf0, 0x9d, 0x93, 0xbd,
+    0xf0, 0x9d, 0x93, 0xae,
+    0xf0, 0x9d, 0x94, 0x81,
+    0xf0, 0x9d, 0x93, 0xbd
+  ]);
+  const decoder = new TextDecoder();
+  assert(decoder.decode(fixture) === "𝓽𝓮𝔁𝓽");
+}
+
+function textDecoderIgnoreBOM() {
+  // deno-fmt-ignore
+  const fixture = new Uint8Array([
+    0xef, 0xbb, 0xbf,
+    0xf0, 0x9d, 0x93, 0xbd,
+    0xf0, 0x9d, 0x93, 0xae,
+    0xf0, 0x9d, 0x94, 0x81,
+    0xf0, 0x9d, 0x93, 0xbd
+  ]);
+  const decoder = new TextDecoder("utf-8", { ignoreBOM: true });
+  assert(decoder.decode(fixture) === "𝓽𝓮𝔁𝓽");
+}
+
+function textDecoderNotBOM() {
+  // deno-fmt-ignore
+  const fixture = new Uint8Array([
+    0xef, 0xbb, 0x89,
+    0xf0, 0x9d, 0x93, 0xbd,
+    0xf0, 0x9d, 0x93, 0xae,
+    0xf0, 0x9d, 0x94, 0x81,
+    0xf0, 0x9d, 0x93, 0xbd
+  ]);
+  const decoder = new TextDecoder("utf-8", { ignoreBOM: true });
+  assert(decoder.decode(fixture) === "ﻉ𝓽𝓮𝔁𝓽");
+}
+
+function textDecoderASCII() {
+  const fixture = new Uint8Array([0x89, 0x95, 0x9f, 0xbf]);
+  const decoder = new TextDecoder("ascii");
+  assert(decoder.decode(fixture) === "‰•Ÿ¿");
+}
+
+function textDecoderErrorEncoding() {
+  let didThrow = false;
+  try {
+    new TextDecoder("foo");
+  } catch (e) {
+    didThrow = true;
+    assert(e.message === "The encoding label provided ('foo') is invalid.");
+  }
+  assert(didThrow);
+}
+
+function textEncoder() {
+  const fixture = "𝓽𝓮𝔁𝓽";
+  const encoder = new TextEncoder();
+  // deno-fmt-ignore
+  assertArrayEquals(Array.from(encoder.encode(fixture)), [
+    0xf0, 0x9d, 0x93, 0xbd,
+    0xf0, 0x9d, 0x93, 0xae,
+    0xf0, 0x9d, 0x94, 0x81,
+    0xf0, 0x9d, 0x93, 0xbd
+  ]);
+}
+
+function textEncodeInto() {
+  const fixture = "text";
+  const encoder = new TextEncoder();
+  const bytes = new Uint8Array(5);
+  const result = encoder.encodeInto(fixture, bytes);
+  assert(result.read === 4);
+  assert(result.written === 4);
+  // deno-fmt-ignore
+  assertArrayEquals(Array.from(bytes), [
+    0x74, 0x65, 0x78, 0x74, 0x00,
+  ]);
+}
+
+function textEncodeInto2() {
+  const fixture = "𝓽𝓮𝔁𝓽";
+  const encoder = new TextEncoder();
+  const bytes = new Uint8Array(17);
+  const result = encoder.encodeInto(fixture, bytes);
+  assert(result.read === 8);
+  assert(result.written === 16);
+  // deno-fmt-ignore
+  assertArrayEquals(Array.from(bytes), [
+    0xf0, 0x9d, 0x93, 0xbd,
+    0xf0, 0x9d, 0x93, 0xae,
+    0xf0, 0x9d, 0x94, 0x81,
+    0xf0, 0x9d, 0x93, 0xbd, 0x00,
+  ]);
+}
+
+function textEncodeInto3() {
+  const fixture = "𝓽𝓮𝔁𝓽";
+  const encoder = new TextEncoder();
+  const bytes = new Uint8Array(5);
+  const result = encoder.encodeInto(fixture, bytes);
+  assert(result.read === 2);
+  assert(result.written === 4);
+  // deno-fmt-ignore
+  assertArrayEquals(Array.from(bytes), [
+    0xf0, 0x9d, 0x93, 0xbd, 0x00,
+  ]);
+}
+
+function textDecoderSharedUint8Array() {
+  const ab = new SharedArrayBuffer(6);
+  const dataView = new DataView(ab);
+  const charCodeA = "A".charCodeAt(0);
+  for (let i = 0; i < ab.byteLength; i++) {
+    dataView.setUint8(i, charCodeA + i);
+  }
+  const ui8 = new Uint8Array(ab);
+  const decoder = new TextDecoder();
+  const actual = decoder.decode(ui8);
+  assert(actual === "ABCDEF");
+}
+
+function textDecoderSharedInt32Array() {
+  const ab = new SharedArrayBuffer(8);
+  const dataView = new DataView(ab);
+  const charCodeA = "A".charCodeAt(0);
+  for (let i = 0; i < ab.byteLength; i++) {
+    dataView.setUint8(i, charCodeA + i);
+  }
+  const i32 = new Int32Array(ab);
+  const decoder = new TextDecoder();
+  const actual = decoder.decode(i32);
+  assert(actual === "ABCDEFGH");
+}
+
+function toStringShouldBeWebCompatibility() {
+  const encoder = new TextEncoder();
+  assert(encoder.toString() === "[object TextEncoder]");
+
+  const decoder = new TextDecoder();
+  assert(decoder.toString() === "[object TextDecoder]");
+}
+
+function main() {
+  btoaSuccess();
+  atobSuccess();
+  atobWithAsciiWhitespace();
+  atobThrows();
+  atobThrows2();
+  btoaFailed();
+  textDecoder2();
+  textDecoderIgnoreBOM();
+  textDecoderNotBOM();
+  textDecoderASCII();
+  textDecoderErrorEncoding();
+  textEncoder();
+  textEncodeInto();
+  textEncodeInto2();
+  textEncodeInto3();
+  textDecoderSharedUint8Array();
+  textDecoderSharedInt32Array();
+  toStringShouldBeWebCompatibility();
+}
+
+main();