jQuery源碼分析之jQuery.event.fix方法五問
問題1:如何調用jQuery.event.fix方法?
event = jQuery.event.fix( event );//回調函數觸發的時候會傳入一個JS的event對象
問題2:那些屬性是鍵盤事件和滑鼠事件共有的屬性?
props: "altKey bubbles cancelable ctrlKey currentTarget eventPhase metaKey relatedTarget shiftKey target timeStamp view which".split(" ")
問題3:鍵盤事件有那些特有的屬性?
keyHooks: {
props: "char charCode key keyCode".split(" "),
filter: function( event, original ) {//event為jQuery.Event對象
// Add which for key events
if ( event.which == null ) {
event.which = original.charCode != null ? original.charCode : original.keyCode;
//如果event的which是空,那麼默認用charCode,如果charCode不存在用keyCode!
}
return event;
}
}
問題4:滑鼠事件有那些專有屬性?
mouseHooks: {
props: "button buttons clientX clientY fromElement offsetX offsetY pageX pageY screenX screenY toElement".split(" "),
filter: function( event, original ) {
var body, eventDoc, doc,
button = original.button,//表示點擊的事件
fromElement = original.fromElement;//表示fromElement
// Calculate pageX/Y if missing and clientX/Y available
if ( event.pageX == null && original.clientX != null ) {
eventDoc = event.target.ownerDocument || document;
doc = eventDoc.documentElement;//這是HTML元素
body = eventDoc.body;//body元素
event.pageX = original.clientX + ( doc && doc.scrollLeft || body && body.scrollLeft || 0 ) - ( doc && doc.clientLeft || body && body.clientLeft || 0 );
event.pageY = original.clientY + ( doc && doc.scrollTop || body && body.scrollTop || 0 ) - ( doc && doc.clientTop || body && body.clientTop || 0 );
}
// Add relatedTarget, if necessary
if ( !event.relatedTarget && fromElement ) {
event.relatedTarget = fromElement === event.target ? original.toElement : fromElement;
}//IE使用了event.fromElement!
// Add which for click: 1 === left; 2 === middle; 3 === right
// Note: button is not normalized, so don"t use it
if ( !event.which && button !== undefined ) {//不建議使用button屬性
event.which = ( button & 1 ? 1 : ( button & 2 ? 3 : ( button & 4 ? 2 : 0 ) ) );
}
return event;
}
}
問題5:如何獲取元素在頁面中的位置,也就是pageX,pageY等屬性?
event.pageX = original.clientX + ( doc && doc.scrollLeft || body && body.scrollLeft || 0 ) - ( doc && doc.clientLeft || body && body.clientLeft || 0 );
event.pageY = original.clientY + ( doc && doc.scrollTop || body && body.scrollTop || 0 ) - ( doc && doc.clientTop || body && body.clientTop || 0 );
我們必須知道jQuery在獲取pageX,pageY的時候減去了body或者documentElement元素的clientLeft和clientTop!
問題6:怎麼知道用戶按住了那一個電腦按鍵?
if ( event.which == null ) {
event.which = original.charCode != null ? original.charCode : original.keyCode;
//如果event的which是空,那麼默認用charCode,如果charCode不存在用keyCode!
}
默認獲取charCode,如果charCode不存在才獲取keyCode,如果需要把按鍵轉化為字元,用
String.fromCharCode(e.which)//e.which是滑鼠和鍵盤公用的事件屬性!
jQuery.event.fix源碼
fix: function( event ) {
//如果是通過jQuery.Event構造函數來完成的,那麼event對象是有倉庫的!
if ( event[ jQuery.expando ] ) {
return event;
}
// Create a writable copy of the event object and normalize some properties
var i, prop, copy,
type = event.type,//獲取JS對象的事件類型
originalEvent = event,//originalEvent保存JS的事件對象
fixHook = this.fixHooks[ type ];
//如果該類型的fixHook不存在,那麼我們自己設置fixHook,如果是滑鼠事件設置為mouseHooks
//如果是鍵盤事件設置為keyHooks!
//rmouseEvent = /^(?:mouse|pointer|contextmenu)|click/,
//rkeyEvent = /^key/
if ( !fixHook ) {
this.fixHooks[ type ] = fixHook =
rmouseEvent.test( type ) ? this.mouseHooks :
rkeyEvent.test( type ) ? this.keyHooks :
{};
}
//props是所有的事件對象都具有的屬性,如果是滑鼠事件那麼把滑鼠事件和他合併,否則就是鍵盤事件屬性合併!
copy = fixHook.props ? this.props.concat( fixHook.props ) : this.props;
//創建jQuery.Event對象
event = new jQuery.Event( originalEvent );
i = copy.length;
//為jQuery.Event對象賦值
while ( i-- ) {
prop = copy[ i ];
event[ prop ] = originalEvent[ prop ];
}
// Support: IE<9
// Fix target property (#1925)
//設置target屬性
if ( !event.target ) {
event.target = originalEvent.srcElement || document;
}
// Support: Chrome 23+, Safari?
// Target should not be a text node (#504, #13143)
//如果target是文本節點,那麼獲取文本節點的父元素!
if ( event.target.nodeType === 3 ) {
event.target = event.target.parentNode;
}
// Support: IE<9
// For mouse/key events, metaKey==false if it"s undefined (#3368, #11328)
event.metaKey = !!event.metaKey;
//用keyHooks或者mouseHooks來過濾event對象!
return fixHook.filter ? fixHook.filter( event, originalEvent ) : event;
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