Adrià Vilanova MartÃnez | f19ea43 | 2024-01-23 20:20:52 +0100 | [diff] [blame] | 1 | // Copyright 2016 The Chromium Authors |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
Copybara | 854996b | 2021-09-07 19:36:02 +0000 | [diff] [blame] | 4 | |
| 5 | var listen; |
| 6 | var unlisten; |
| 7 | var unlistenByKey; |
| 8 | |
| 9 | (function() { |
| 10 | let listeners = {}; |
| 11 | let nextId = 0; |
| 12 | |
| 13 | function getHashCode_(obj) { |
| 14 | if (obj.listen_hc_ == null) { |
| 15 | obj.listen_hc_ = ++nextId; |
| 16 | } |
| 17 | return obj.listen_hc_; |
| 18 | } |
| 19 | |
| 20 | /** |
| 21 | * Takes a node, event, listener, and capture flag to create a key |
| 22 | * to identify the tuple in the listeners hash. |
| 23 | * |
| 24 | * @param {Element} node The node to listen to events on. |
| 25 | * @param {string} event The name of the event without the "on" prefix. |
| 26 | * @param {Function} listener A function to call when the event occurs. |
| 27 | * @param {boolean} opt_useCapture In DOM-compliant browsers, this determines |
| 28 | * whether the listener is fired during the |
| 29 | * capture or bubble phase of the event. |
| 30 | * @return {string} key to identify this tuple in the listeners hash. |
| 31 | */ |
| 32 | function createKey_(node, event, listener, opt_useCapture) { |
| 33 | let nodeHc = getHashCode_(node); |
| 34 | let listenerHc = getHashCode_(listener); |
| 35 | opt_useCapture = !!opt_useCapture; |
| 36 | let key = nodeHc + '_' + event + '_' + listenerHc + '_' + opt_useCapture; |
| 37 | return key; |
| 38 | } |
| 39 | |
| 40 | /** |
| 41 | * Adds an event listener to a DOM node for a specific event. |
| 42 | * |
| 43 | * Listen() and unlisten() use an indirect lookup of listener functions |
| 44 | * to avoid circular references between DOM (in IE) or XPCOM (in Mozilla) |
| 45 | * objects which leak memory. This makes it easier to write OO |
| 46 | * Javascript/DOM code. |
| 47 | * |
| 48 | * Examples: |
| 49 | * listen(myButton, 'click', myHandler, true); |
| 50 | * listen(myButton, 'click', this.myHandler.bind(this), true); |
| 51 | * |
| 52 | * @param {Element} node The node to listen to events on. |
| 53 | * @param {string} event The name of the event without the "on" prefix. |
| 54 | * @param {Function} listener A function to call when the event occurs. |
| 55 | * @param {boolean} opt_useCapture In DOM-compliant browsers, this determines |
| 56 | * whether the listener is fired during the |
| 57 | * capture or bubble phase of the event. |
| 58 | * @return {string} a unique key to indentify this listener. |
| 59 | */ |
| 60 | listen = function(node, event, listener, opt_useCapture) { |
| 61 | let key = createKey_(node, event, listener, opt_useCapture); |
| 62 | |
| 63 | // addEventListener does not allow multiple listeners |
| 64 | if (key in listeners) { |
| 65 | return key; |
| 66 | } |
| 67 | |
| 68 | let proxy = handleEvent.bind(null, key); |
| 69 | listeners[key] = { |
| 70 | listener: listener, |
| 71 | proxy: proxy, |
| 72 | event: event, |
| 73 | node: node, |
| 74 | useCapture: opt_useCapture, |
| 75 | }; |
| 76 | |
| 77 | if (node.addEventListener) { |
| 78 | node.addEventListener(event, proxy, opt_useCapture); |
| 79 | } else if (node.attachEvent) { |
| 80 | node.attachEvent('on' + event, proxy); |
| 81 | } else { |
| 82 | throw new Error('Node {' + node + '} does not support event listeners.'); |
| 83 | } |
| 84 | |
| 85 | return key; |
| 86 | }; |
| 87 | |
| 88 | /** |
| 89 | * Removes an event listener which was added with listen(). |
| 90 | * |
| 91 | * @param {Element} node The node to stop listening to events on. |
| 92 | * @param {string} event The name of the event without the "on" prefix. |
| 93 | * @param {Function} listener The listener function to remove. |
| 94 | * @param {boolean} opt_useCapture In DOM-compliant browsers, this determines |
| 95 | * whether the listener is fired during the |
| 96 | * capture or bubble phase of the event. |
| 97 | * @return {boolean} indicating whether the listener was there to remove. |
| 98 | */ |
| 99 | unlisten = function(node, event, listener, opt_useCapture) { |
| 100 | let key = createKey_(node, event, listener, opt_useCapture); |
| 101 | |
| 102 | return unlistenByKey(key); |
| 103 | }; |
| 104 | |
| 105 | /** |
| 106 | * Variant of {@link unlisten} that takes a key that was returned by |
| 107 | * {@link listen} and removes that listener. |
| 108 | * |
| 109 | * @param {string} key Key of event to be unlistened. |
| 110 | * @return {boolean} indicating whether it was there to be removed. |
| 111 | */ |
| 112 | unlistenByKey = function(key) { |
| 113 | if (!(key in listeners)) { |
| 114 | return false; |
| 115 | } |
| 116 | let listener = listeners[key]; |
| 117 | let proxy = listener.proxy; |
| 118 | let event = listener.event; |
| 119 | let node = listener.node; |
| 120 | let useCapture = listener.useCapture; |
| 121 | |
| 122 | if (node.removeEventListener) { |
| 123 | node.removeEventListener(event, proxy, useCapture); |
| 124 | } else if (node.detachEvent) { |
| 125 | node.detachEvent('on' + event, proxy); |
| 126 | } |
| 127 | |
| 128 | delete listeners[key]; |
| 129 | return true; |
| 130 | }; |
| 131 | |
| 132 | /** |
| 133 | * The function which is actually called when the DOM event occurs. This |
| 134 | * function is a proxy for the real listener the user specified. |
| 135 | */ |
| 136 | function handleEvent(key) { |
| 137 | // pass all arguments which were sent to this function except listenerID |
| 138 | // on to the actual listener. |
| 139 | let args = Array.prototype.splice.call(arguments, 1, arguments.length); |
| 140 | return listeners[key].listener.apply(null, args); |
| 141 | } |
| 142 | })(); |