XMLHttpRequestEventTarget: error event

Note: This feature is available inWeb Workers, except forService Workers.

Theerror event is fired when the request encountered an error.

Syntax

Use the event name in methods likeaddEventListener(), or set an event handler property.

addEventListener("error", (event) => { })onerror = (event) => { }

Event type

AProgressEvent. Inherits fromEvent.

Event properties

In addition to the properties listed below, properties from the parent interface,Event, are available.

lengthComputableRead only: A boolean flag indicating if the total work to be done, and the amount of work already done, by the underlying process is calculable. In other words, it tells if the progress is measurable or not.
loadedRead only: A 64-bit unsigned integer value indicating the amount of work already performed by the underlying process. The proportion of work done can be calculated by dividing the value of this property bytotal. When downloading a resource using HTTP, this only counts the body of the HTTP message, and doesn't include headers and other overhead.
totalRead only: A 64-bit unsigned integer representing the total amount of work that the underlying process is in the progress of performing. When downloading a resource using HTTP, this is theContent-Length (the size of the body of the message), and doesn't include the headers and other overhead.

Examples

Usage with XMLHttpRequest

HTML

html

<div>  <input       type="button"    name="xhr"    value="Click to start XHR (success)" />  <input       type="button"    name="xhr"    value="Click to start XHR (error)" />  <input       type="button"    name="xhr"    value="Click to start XHR (abort)" /></div><textarea readonly></textarea>

.event-log {  width: 25rem;  height: 4rem;  border: 1px solid black;  margin: 0.5rem;  padding: 0.2rem;}input {  width: 11rem;  margin: 0.5rem;}

JavaScript

const xhrButtonSuccess = document.querySelector(".xhr.success");const xhrButtonError = document.querySelector(".xhr.error");const xhrButtonAbort = document.querySelector(".xhr.abort");const log = document.querySelector(".event-log");function handleEvent(e) {  log.textContent = `${log.textContent}${e.type}: ${e.loaded} bytes transferred\n`;}function addListeners(xhr) {  xhr.addEventListener("loadstart", handleEvent);  xhr.addEventListener("load", handleEvent);  xhr.addEventListener("loadend", handleEvent);  xhr.addEventListener("progress", handleEvent);  xhr.addEventListener("error", handleEvent);  xhr.addEventListener("abort", handleEvent);}function runXHR(url) {  log.textContent = "";  const xhr = new XMLHttpRequest();  addListeners(xhr);  xhr.open("GET", url);  xhr.send();  return xhr;}xhrButtonSuccess.addEventListener("click", () => {  runXHR("example-image.jpg");});xhrButtonError.addEventListener("click", () => {  runXHR("https://example.com/notfound.jpg");});xhrButtonAbort.addEventListener("click", () => {  runXHR("example-image.jpg").abort();});

Result

Usage with XMLHttpRequestUpload

You can use theerror event to detect a problem with the upload. For a complete code example that uploads a file and displays a progress bar, see the mainXMLHttpRequestUpload page.

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