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node-creation-observer

Callback binding for HTML Node creation events

当前为 2016-12-18 提交的版本，查看 最新版本。

此脚本不应直接安装。它是供其他脚本使用的外部库，要使用该库请加入元指令 // @require https://update.cn-greasyfork.org/scripts/19857/164039/node-creation-observer.js 

  1. /**
  2.  * https://github.com/soufianesakhi/node-creation-observer-js
  3.  * MIT licensed
  4.  * Copyright (c) 2016 Soufiane Sakhi
  5.  */
  6. var NodeCreationObserver = function () {
  7.     var mutationObserver = null;
  8.     var observedNodeAttribute = "node-creation-observer";
  9.     var listeners = {};
  10.     var options = {
  11.         childList: true,
  12.         subtree: true
  13.     };
  14.     var ListenerContext = (function () {
  15.         function ListenerContext(removeOnFirstMatch) {
  16.             this.callbacks = [];
  17.             this.removeOnFirstMatch = removeOnFirstMatch == undefined ? false : removeOnFirstMatch;
  18.         }
  19.         return ListenerContext;
  20.     }());
  21.     function onMutationCallback() {
  22.         Object.keys(listeners).forEach(function (selector) {
  23.             invokeCallbacks(selector);
  24.         });
  25.     }
  26.     function invokeCallbacks(selector) {
  27.         var callbacks = listeners[selector].callbacks;
  28.         var elements = document.querySelectorAll(selector);
  29.         var newElements = filterNewElements(elements);
  30.         if (newElements.length > 0) {
  31.             if (listeners[selector].removeOnFirstMatch) {
  32.                 removeListener(selector);
  33.             }
  34.             newElements.forEach(function (element) {
  35.                 callbacks.forEach(function (callback) {
  36.                     callback.call(element, element);
  37.                 });
  38.             });
  39.         }
  40.     }
  41.     function filterNewElements(elements) {
  42.         var newElements = [];
  43.         for (var i = 0; i < elements.length; i++) {
  44.             var element = elements[i];
  45.             var attr = element.getAttribute(observedNodeAttribute);
  46.             if (attr == null) {
  47.                 element.setAttribute(observedNodeAttribute, "1");
  48.                 newElements.push(element);
  49.             }
  50.         }
  51.         ;
  52.         return newElements;
  53.     }
  54.     function observe() {
  55.         if (mutationObserver == null) {
  56.             mutationObserver = new MutationObserver(onMutationCallback);
  57.             mutationObserver.observe(document.documentElement, options);
  58.         }
  59.     }
  60.     function removeListener(selector) {
  61.         delete listeners[selector];
  62.         if (Object.keys(listeners).length == 0) {
  63.             stopObserving();
  64.         }
  65.     }
  66.     function stopObserving() {
  67.         if (mutationObserver != null) {
  68.             mutationObserver.disconnect();
  69.             mutationObserver = null;
  70.         }
  71.     }
  72.     return {
  73.         onCreation: function (selector, callback, removeOnFirstMatch) {
  74.             if (!listeners[selector]) {
  75.                 listeners[selector] = new ListenerContext(removeOnFirstMatch);
  76.             }
  77.             listeners[selector].callbacks.push(callback);
  78.             observe();
  79.             if (document.querySelector(selector) != null) {
  80.                 invokeCallbacks(selector);
  81.             }
  82.         },
  83.         remove: removeListener,
  84.         stop: function () {
  85.             listeners = {};
  86.             stopObserving();
  87.         }
  88.     };
  89. }();