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window.addeventjs事件驅(qū)動(dòng)函數(shù)集合addEvent等

更新時(shí)間：2008年02月19日 11:37:31 作者：

addEvent()、removeEvent()、handleEvent()、fixEvent()[

// written by Dean Edwards, 2005
// with input from Tino Zijdel, Matthias Miller, Diego Perini

// http://dean.edwards.name/weblog/2005/10/add-event/

function addEvent(element, type, handler) {
  if (element.addEventListener) {
    element.addEventListener(type, handler, false);
  } else {
    // assign each event handler a unique ID
    if (!handler.$$guid) handler.$$guid = addEvent.guid++;
    // create a hash table of event types for the element
    if (!element.events) element.events = {};
    // create a hash table of event handlers for each element/event pair
    var handlers = element.events[type];
    if (!handlers) {
      handlers = element.events[type] = {};
      // store the existing event handler (if there is one)
      if (element["on" + type]) {
        handlers[0] = element["on" + type];
      }
    }
    // store the event handler in the hash table
    handlers[handler.$$guid] = handler;
    // assign a global event handler to do all the work
    element["on" + type] = handleEvent;
  }
};
// a counter used to create unique IDs
addEvent.guid = 1;

function removeEvent(element, type, handler) {
  if (element.removeEventListener) {
    element.removeEventListener(type, handler, false);
  } else {
    // delete the event handler from the hash table
    if (element.events && element.events[type]) {
      delete element.events[type][handler.$$guid];
    }
  }
};

function handleEvent(event) {
  var returnValue = true;
  // grab the event object (IE uses a global event object)
  event = event || fixEvent(((this.ownerDocument || this.document || this).parentWindow || window).event);
  // get a reference to the hash table of event handlers
  var handlers = this.events[event.type];
  // execute each event handler
  for (var i in handlers) {
    this.$$handleEvent = handlers[i];
    if (this.$$handleEvent(event) === false) {
      returnValue = false;
    }
  }
  return returnValue;
};

function fixEvent(event) {
  // add W3C standard event methods
  event.preventDefault = fixEvent.preventDefault;
  event.stopPropagation = fixEvent.stopPropagation;
  return event;
};
fixEvent.preventDefault = function() {
  this.returnValue = false;
};
fixEvent.stopPropagation = function() {
  this.cancelBubble = true;
};

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