AbortController

AbortController()

Creates a new AbortController object instance.

AbortController.signal Read only

Returns an AbortSignal object instance, which can be used to communicate with, or to abort, an asynchronous operation.

AbortController.abort()

Aborts an asynchronous operation before it has completed. This is able to abort fetch requests, consumption of any response bodies, and streams.

In the following snippet, we aim to download a video using the Fetch API.

We first create a controller using the AbortController() constructor, then grab a reference to its associated AbortSignal object using the AbortController.signal property.

When the fetch request is initiated, we pass in the AbortSignal as an option inside the request's options object (the {signal} below). This associates the signal and controller with the fetch request and allows us to abort it by calling AbortController.abort(), as seen below in the second event listener.

When abort() is called, the fetch() promise rejects with a DOMException named AbortError.

let controller;
const url = "video.mp4";

const downloadBtn = document.querySelector(".download");
const abortBtn = document.querySelector(".abort");

downloadBtn.addEventListener("click", fetchVideo);

abortBtn.addEventListener("click", () => {
  if (controller) {
    controller.abort();
    console.log("Download aborted");
  }
});

async function fetchVideo() {
  controller = new AbortController();
  const signal = controller.signal;

  try {
    const response = await fetch(url, { signal });
    console.log("Download complete", response);
    // process response further
  } catch (err) {
    console.error(`Download error: ${err.message}`);
  }
}

If the request is aborted after the fetch() call has been fulfilled but before the response body has been read, then attempting to read the response body will reject with an AbortError exception.

async function get() {
  const controller = new AbortController();
  const request = new Request("https://example.org/get", {
    signal: controller.signal,
  });

  const response = await fetch(request);
  controller.abort();
  // The next line will throw `AbortError`
  const text = await response.text();
  console.log(text);
}

You can find a full working example on GitHub; you can also see it running live.

• Fetch API
• Abortable Fetch by Jake Archibald