b38dea0597
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60 lines
1.7 KiB
JavaScript
60 lines
1.7 KiB
JavaScript
'use strict';
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/* exported eventSafety */
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/**
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* Listens for an event to fire _once_ or a timeout to expire.
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* This is generally used for things which are waiting on transitions
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* as it's sometimes possible to miss the transitionend event.
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* This should not be necessary once we have web animations as they
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* will guarantee that a callback is fired.
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*
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* Usage:
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*
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* eventSafety(window, 'transitionend', callback, 400);
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*
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* eventSafety(window, 'transitionend', 400).then(() => { ... });
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*
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* @param {Object} obj
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* Object to listen to the event on.
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* @param {String} event
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* The name of the event.
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* @param {Function} callback
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Optional; called after the event is fired.
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* @param {Integer} timeout The duration of the safety timeout.
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*
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* @return {Promise}
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* A promise that will never reject.
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*/
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function eventSafety(obj, event, callback, timeout) {
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if (typeof callback === 'number') {
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timeout = callback;
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callback = null;
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}
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if (!timeout) {
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throw new Error('You must pass a valid timeout value to `eventSafety`.');
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}
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return new Promise((resolve) => {
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var finishTimeout;
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function done(e) {
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// Both "transitionend" and "animationend" events bubble by default;
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// ignore them here if they're not targeted on the element we care about.
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if (e && e.target !== obj &&
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(e.type === 'transitionend' || e.type === 'animationend')) {
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return;
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}
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clearTimeout(finishTimeout);
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obj.removeEventListener(event, done);
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if (callback) {
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/*jshint validthis:true */
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resolve(callback.apply(this, arguments));
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} else {
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resolve(e);
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}
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}
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finishTimeout = setTimeout(done, timeout);
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obj.addEventListener(event, done);
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});
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}
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