XMLHttpRequestUpload

Note: This feature is available in Web Workers, except for Service Workers.

The XMLHttpRequestUpload interface represents the upload process for a specific XMLHttpRequest. It is an opaque object that represents the underlying, browser-dependent, upload process. It is an XMLHttpRequestEventTarget and can be obtained by calling XMLHttpRequest.upload.

EventTarget XMLHttpRequestEventTarget XMLHttpRequestUpload

Instance properties

This interface has no specific property, but inherits the properties of XMLHttpRequestEventTarget and of EventTarget.

Instance methods

This interface has no specific method, but inherits the methods of XMLHttpRequestEventTarget and of EventTarget.

Events

abort

Fired when a request has been aborted, for example because the program called XMLHttpRequest.abort(). Also available via the onabort event handler property.

error

Fired when the request encountered an error. Also available via the onerror event handler property.

load

Fired when a request transaction completes successfully. Also available via the onload event handler property.

loadend

Fired when a request has completed, whether successfully (after load) or unsuccessfully (after abort or error). Also available via the onloadend event handler property.

loadstart

Fired when a request has started to load data. Also available via the onloadstart event handler property.

progress

Fired periodically when a request receives more data. Also available via the onprogress event handler property.

timeout

Fired when progress is terminated due to preset time expiring. Also available via the ontimeout event handler property.

Examples

Uploading a file with a timeout

This allows you to upload a file to a server; it displays a progress bar while the upload is happening as well as a message with the progress and the results, success or failure. An abort button allows to stop an upload.

HTML

html
<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width" />
    <title>XMLHttpRequestUpload test</title>
    <link rel="stylesheet" href="xhrupload_test.css" />
    <script src="xhrupload_test.js"></script>
  </head>
  <body>
    <main>
      <h1>Upload a file</h1>
      <p>
        <label for="file">File to upload</label><input type="file" id="file" />
      </p>
      <p>
        <progress />
      </p>
      <p>
        <output></output>
      </p>
      <p>
        <button disabled id="abort">Abort</button>
      </p>
    </main>
  </body>
</html>

CSS

css
body {
  background-color: lightblue;
}

main {
  margin: 50px auto;
  text-align: center;
}

#file {
  display: none;
}

label[for="file"] {
  background-color: lightgrey;
  padding: 10px 10px;
}

progress {
  display: none;
}

progress.visible {
  display: inline;
}

JavaScript

js
addEventListener("DOMContentLoaded", () => {
  const fileInput = document.getElementById("file");
  const progressBar = document.querySelector("progress");
  const log = document.querySelector("output");
  const abortButton = document.getElementById("abort");

  fileInput.addEventListener("change", () => {
    const xhr = new XMLHttpRequest();
    xhr.timeout = 2000; // 2 seconds

    // Link abort button
    abortButton.addEventListener(
      "click",
      () => {
        xhr.abort();
      },
      { once: true },
    );

    // When the upload starts, we display the progress bar
    xhr.upload.addEventListener("loadstart", (event) => {
      progressBar.classList.add("visible");
      progressBar.value = 0;
      progressBar.max = event.total;
      log.textContent = "Uploading (0%)…";
      abortButton.disabled = false;
    });

    // Each time a progress event is received, we update the bar
    xhr.upload.addEventListener("progress", (event) => {
      progressBar.value = event.loaded;
      log.textContent = `Uploading (${(
        (event.loaded / event.total) *
        100
      ).toFixed(2)}%)…`;
    });

    // When the upload is finished, we hide the progress bar.
    xhr.upload.addEventListener("loadend", (event) => {
      progressBar.classList.remove("visible");
      if (event.loaded !== 0) {
        log.textContent = "Upload finished.";
      }
      abortButton.disabled = true;
    });

    // In case of an error, an abort, or a timeout, we hide the progress bar
    // Note that these events can be listened to on the xhr object too
    function errorAction(event) {
      progressBar.classList.remove("visible");
      log.textContent = `Upload failed: ${event.type}`;
    }
    xhr.upload.addEventListener("error", errorAction);
    xhr.upload.addEventListener("abort", errorAction);
    xhr.upload.addEventListener("timeout", errorAction);

    // Build the payload
    const fileData = new FormData();
    fileData.append("file", fileInput.files[0]);

    // Theoretically, event listeners could be set after the open() call
    // but browsers are buggy here
    xhr.open("POST", "upload_test.php", true);

    // Note that the event listener must be set before sending (as it is a preflighted request)
    xhr.send(fileData);
  });
});

Specifications

Specification
XMLHttpRequest Standard
# xmlhttprequestupload

Browser compatibility

BCD tables only load in the browser

See also