3 files changed, 56 insertions, 1 deletions
diff --git a/runtime/js/01_async_context.js b/runtime/js/01_async_context.js
new file mode 100644
index 000000000..9c0236fbe
--- /dev/null
+++ b/runtime/js/01_async_context.js
@@ -0,0 +1,45 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+import { primordials } from "ext:core/mod.js";
+import { op_get_extras_binding_object } from "ext:core/ops";
+
+const {
+  SafeWeakMap,
+} = primordials;
+
+const {
+  getContinuationPreservedEmbedderData,
+  setContinuationPreservedEmbedderData,
+} = op_get_extras_binding_object();
+
+let counter = 0;
+
+export const getAsyncContext = getContinuationPreservedEmbedderData;
+export const setAsyncContext = setContinuationPreservedEmbedderData;
+
+export class AsyncVariable {
+  #id = counter++;
+  #data = new SafeWeakMap();
+
+  enter(value) {
+    const previousContextMapping = getAsyncContext();
+    const entry = { id: this.#id };
+    const asyncContextMapping = {
+      __proto__: null,
+      ...previousContextMapping,
+      [this.#id]: entry,
+    };
+    this.#data.set(entry, value);
+    setAsyncContext(asyncContextMapping);
+    return previousContextMapping;
+  }
+
+  get() {
+    const current = getAsyncContext();
+    const entry = current?.[this.#id];
+    if (entry) {
+      return this.#data.get(entry);
+    }
+    return undefined;
+  }
+}
diff --git a/runtime/ops/runtime.rs b/runtime/ops/runtime.rs
index 306e6ce8f..b52a23f30 100644
--- a/runtime/ops/runtime.rs
+++ b/runtime/ops/runtime.rs
@@ -2,13 +2,14 @@
 
 use deno_core::error::AnyError;
 use deno_core::op2;
+use deno_core::v8;
 use deno_core::ModuleSpecifier;
 use deno_core::OpState;
 use deno_permissions::PermissionsContainer;
 
 deno_core::extension!(
   deno_runtime,
-  ops = [op_main_module, op_ppid],
+  ops = [op_main_module, op_ppid, op_get_extras_binding_object],
   options = { main_module: ModuleSpecifier },
   state = |state, options| {
     state.put::<ModuleSpecifier>(options.main_module);
@@ -94,3 +95,11 @@ pub fn op_ppid() -> i64 {
     parent_id().into()
   }
 }
+
+#[op2]
+pub fn op_get_extras_binding_object<'a>(
+  scope: &mut v8::HandleScope<'a>,
+) -> v8::Local<'a, v8::Value> {
+  let context = scope.get_current_context();
+  context.get_extras_binding_object(scope).into()
+}
diff --git a/runtime/shared.rs b/runtime/shared.rs
index 1b2136c63..185cbc0a9 100644
--- a/runtime/shared.rs
+++ b/runtime/shared.rs
@@ -38,6 +38,7 @@ extension!(runtime,
     dir "js",
     "01_errors.js",
     "01_version.ts",
+    "01_async_context.js",
     "06_util.js",
     "10_permissions.js",
     "11_workers.js",