runtime.lastError

Syntax

var myError = chrome.runtime.lastError;  // null or Error object

This API is also available as browser.runtime.lastError.

Value

An Error object representing the error. The message property is a string with a human-readable description of the error . If lastError has not been set, the value is null.

Examples

There are two different ways add-ons can call asynchronous functions:

• By passing in a callback to the function, which is called with the function's result.
• By omitting the callback and using the browser namespace, in which case the function will return a Promise.

In the first case, if the function can set lastError you should check it in the callback. For example:

function logCookie(c) {
  if (chrome.runtime.lastError) {
    console.error(chrome.runtime.lastError);
  } else {
    console.log(c);
  }
}

chrome.cookies.set(
  {url: "https://developer.mozilla.org/"},
  logCookie
);

In the second case, lastError will be passed into the second argument of Promise.then():

function logCookie(c) {
  console.log(c);
}

function logError(e) {
  console.error(e);
}

var setCookie = browser.cookies.set(
  {url: "https://developer.mozilla.org/"}
);

setCookie.then(logCookie, logError);

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Compatibility notes

Chrome

• lastError is not an Error object. Instead, it is a plain Object with the error text as the string value of the 'message' property.

Opera

• lastError is not an Error object. Instead, it is a plain Object with the error text as the string value of the 'message' property.

Example add-ons

• context-menu-demo
• latest-download

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