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webRequest.StreamFilter.onstop

An event handler that will be called when the stream has no more data to deliver. In the event handler you can still call filter functions such as write(), disconnect(), or close().

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
onstop No No 57 ? No No ? ? 57 ? No ?

Examples

This example will append "extra stuff" to the response:

function listener(details) {
  const filter = browser.webRequest.filterResponseData(details.requestId);
  const encoder = new TextEncoder();

  filter.ondata = (event) => {
    // pass through all the response data
    filter.write(event.data);
  };

  filter.onstop = (event) => {
    filter.write(encoder.encode("extra stuff"));
    filter.disconnect();
  };
}

browser.webRequest.onBeforeRequest.addListener(
  listener,
  { urls: ["https://example.com/*"], types: ["main_frame"] },
  ["blocking"]
);

Here's another version of the example above:

function listener(details) {
  const filter = browser.webRequest.filterResponseData(details.requestId);
  const encoder = new TextEncoder();

  const data = [];
  filter.ondata = (event) => {
    data.push(event.data);
  };

  filter.onstop = (event) => {
    for (const buffer of data) {
      filter.write(buffer);
    }
    filter.write(encoder.encode("extra stuff"));
    filter.close();
  };
}

browser.webRequest.onBeforeRequest.addListener(
  listener,
  { urls: ["https://example.com/"], types: ["main_frame"] },
  ["blocking"]
);

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https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/webRequest/StreamFilter/onstop