1 files changed, 78 insertions, 0 deletions
diff --git a/cli/js/web/util.ts b/cli/js/web/util.ts
new file mode 100644
index 000000000..b0a050973
--- /dev/null
+++ b/cli/js/web/util.ts
@@ -0,0 +1,78 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+export type TypedArray = Uint8Array | Float32Array | Int32Array;
+const TypedArrayConstructor = Object.getPrototypeOf(Uint8Array);
+export function isTypedArray(x: unknown): x is TypedArray {
+  return x instanceof TypedArrayConstructor;
+}
+
+// @internal
+export function requiredArguments(
+  name: string,
+  length: number,
+  required: number
+): void {
+  if (length < required) {
+    const errMsg = `${name} requires at least ${required} argument${
+      required === 1 ? "" : "s"
+    }, but only ${length} present`;
+    throw new TypeError(errMsg);
+  }
+}
+
+// @internal
+export function immutableDefine(
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  o: any,
+  p: string | number | symbol,
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  value: any
+): void {
+  Object.defineProperty(o, p, {
+    value,
+    configurable: false,
+    writable: false
+  });
+}
+
+// Returns values from a WeakMap to emulate private properties in JavaScript
+export function getPrivateValue<
+  K extends object,
+  V extends object,
+  W extends keyof V
+>(instance: K, weakMap: WeakMap<K, V>, key: W): V[W] {
+  if (weakMap.has(instance)) {
+    return weakMap.get(instance)![key];
+  }
+  throw new TypeError("Illegal invocation");
+}
+
+/**
+ * Determines whether an object has a property with the specified name.
+ * Avoid calling prototype builtin `hasOwnProperty` for two reasons:
+ *
+ * 1. `hasOwnProperty` is defined on the object as something else:
+ *
+ *      const options = {
+ *        ending: 'utf8',
+ *        hasOwnProperty: 'foo'
+ *      };
+ *      options.hasOwnProperty('ending') // throws a TypeError
+ *
+ * 2. The object doesn't inherit from `Object.prototype`:
+ *
+ *       const options = Object.create(null);
+ *       options.ending = 'utf8';
+ *       options.hasOwnProperty('ending'); // throws a TypeError
+ *
+ * @param obj A Object.
+ * @param v A property name.
+ * @see https://eslint.org/docs/rules/no-prototype-builtins
+ * @internal
+ */
+export function hasOwnProperty<T>(obj: T, v: PropertyKey): boolean {
+  if (obj == null) {
+    return false;
+  }
+  return Object.prototype.hasOwnProperty.call(obj, v);
+}