1 第一代事件系統
Eean wdwrad 大神的addEvent.js.當然最原始的jQuery事件系統也是照抄過來的.
function addEvent(element, type, handler) {
// 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.$$guid] = handler;
// assign a global event handler to do all the work
element["on" + type] = handleEvent;
};
// a counter used to create unique IDs
addEvent.guid = 1;
function removeEvent(element, type, handler) {
// delete the event handler from the hash table
if (element.events && element.events[type]) {
delete element.events[type][handler.$$guid];
}
};
function handleEvent(event) {
// grab the event object (IE uses a global event object)
event = event || 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.$$handleEvent = handlers[i];
this.$$handleEvent(event);
}
};
當然,這由於是最初的版本,自然還沒有引入緩存系統。由於是將回調事件handler直接綁定在元素上,可能引發循環引用,導致內存泄漏。
也有在iframe中事件對象不對的問題。
在ED大神的博客的第54條回覆中,直接引發了jquery的緩存機制的產生,建議給元素分配一個UUID,所有的回調都放到一個對象中去存儲。
看到司徒大神的一段對於oninput事件的處理:
if (W3C) { //先執行W3C
element.addEventListener("input", updateVModel)
data.rollback = function() {
element.removeEventListener("input", updateVModel)
}
} else {
removeFn = function(e) {
if (e.propertyName === "value") {
updateVModel()
}
}
element.attachEvent("onpropertychange", removeFn)
data.rollback = function() {
element.detachEvent("onpropertychange", removeFn)
}
}
if (DOC.documentMode === 9) { // IE9 無法在切剪中同步VM
var selectionchange = function(e) {
if (e.type === "focus") {
DOC.addEventListener("selectionchange", updateVModel)
} else {
DOC.removeEventListener("selectionchange", updateVModel)
}
}
element.addEventListener("focus", selectionchange)
element.addEventListener("blur", selectionchange)
var rollback = data.rollback
data.rollback = function() {
rollback()
element.removeEventListener("focus", selectionchange)
element.removeEventListener("blur", selectionchange)
}
}
}
防止循環引用的產生。