isEventSupported.js
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/**
* Copyright 2013-2015, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
* @providesModule isEventSupported
*/
'use strict';
var ExecutionEnvironment = require('./ExecutionEnvironment');
var useHasFeature;
if (ExecutionEnvironment.canUseDOM) {
useHasFeature =
document.implementation &&
document.implementation.hasFeature &&
// always returns true in newer browsers as per the standard.
// @see http://dom.spec.whatwg.org/#dom-domimplementation-hasfeature
document.implementation.hasFeature('', '') !== true;
}
/**
* Checks if an event is supported in the current execution environment.
*
* NOTE: This will not work correctly for non-generic events such as `change`,
* `reset`, `load`, `error`, and `select`.
*
* Borrows from Modernizr.
*
* @param {string} eventNameSuffix Event name, e.g. "click".
* @param {?boolean} capture Check if the capture phase is supported.
* @return {boolean} True if the event is supported.
* @internal
* @license Modernizr 3.0.0pre (Custom Build) | MIT
*/
function isEventSupported(eventNameSuffix, capture) {
if (!ExecutionEnvironment.canUseDOM ||
capture && !('addEventListener' in document)) {
return false;
}
var eventName = 'on' + eventNameSuffix;
var isSupported = eventName in document;
if (!isSupported) {
var element = document.createElement('div');
element.setAttribute(eventName, 'return;');
isSupported = typeof element[eventName] === 'function';
}
if (!isSupported && useHasFeature && eventNameSuffix === 'wheel') {
// This is the only way to test support for the `wheel` event in IE9+.
isSupported = document.implementation.hasFeature('Events.wheel', '3.0');
}
return isSupported;
}
module.exports = isEventSupported;