1 files changed, 58 insertions, 0 deletions
diff --git a/cli/js/web/abort_signal.ts b/cli/js/web/abort_signal.ts
new file mode 100644
index 000000000..b741d6534
--- /dev/null
+++ b/cli/js/web/abort_signal.ts
@@ -0,0 +1,58 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { EventImpl } from "./event.ts";
+import { EventTargetImpl } from "./event_target.ts";
+
+export const add = Symbol("add");
+export const signalAbort = Symbol("signalAbort");
+export const remove = Symbol("remove");
+
+export class AbortSignalImpl extends EventTargetImpl implements AbortSignal {
+  #aborted?: boolean;
+  #abortAlgorithms = new Set<() => void>();
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  onabort: ((this: AbortSignal, ev: Event) => any) | null = null;
+
+  [add](algorithm: () => void): void {
+    this.#abortAlgorithms.add(algorithm);
+  }
+
+  [signalAbort](): void {
+    if (this.#aborted) {
+      return;
+    }
+    this.#aborted = true;
+    for (const algorithm of this.#abortAlgorithms) {
+      algorithm();
+    }
+    this.#abortAlgorithms.clear();
+    this.dispatchEvent(new EventImpl("abort"));
+  }
+
+  [remove](algorithm: () => void): void {
+    this.#abortAlgorithms.delete(algorithm);
+  }
+
+  constructor() {
+    super();
+    this.addEventListener("abort", (evt: Event) => {
+      const { onabort } = this;
+      if (typeof onabort === "function") {
+        onabort.call(this, evt);
+      }
+    });
+  }
+
+  get aborted(): boolean {
+    return Boolean(this.#aborted);
+  }
+
+  get [Symbol.toStringTag](): string {
+    return "AbortSignal";
+  }
+}
+
+Object.defineProperty(AbortSignalImpl, "name", {
+  value: "AbortSignal",
+  configurable: true,
+});