зеркало из https://github.com/mozilla/gecko-dev.git
38 строки
1.4 KiB
JavaScript
38 строки
1.4 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
"use strict";
|
|
|
|
/**
|
|
* Helpers for async functions. Async functions are generator functions that are
|
|
* run by Tasks. An async function returns a Promise for the resolution of the
|
|
* function. When the function returns, the promise is resolved with the
|
|
* returned value. If it throws the promise rejects with the thrown error.
|
|
*
|
|
* See Task documentation at https://developer.mozilla.org/en-US/docs/Mozilla/JavaScript_code_modules/Task.jsm.
|
|
*/
|
|
|
|
/**
|
|
* Adds an event listener to the given element, and then removes its event
|
|
* listener once the event is called, returning the event object as a promise.
|
|
* @param Element element
|
|
* The DOM element to listen on
|
|
* @param String event
|
|
* The name of the event type to listen for
|
|
* @param Boolean useCapture
|
|
* Should we initiate the capture phase?
|
|
* @return Promise
|
|
* The promise resolved with the event object when the event first
|
|
* happens
|
|
*/
|
|
exports.listenOnce = function listenOnce(element, event, useCapture) {
|
|
return new Promise(function(resolve, reject) {
|
|
const onEvent = function(ev) {
|
|
element.removeEventListener(event, onEvent, useCapture);
|
|
resolve(ev);
|
|
};
|
|
element.addEventListener(event, onEvent, useCapture);
|
|
});
|
|
};
|