事件测试(4项)
jQuery.support = (function() {
var support,
all,
a,
select,
opt,
input,
marginDiv,
fragment,
tds,
events,
eventName,
i,
isSupported,
div = document.createElement( "div" ),
documentElement = document.documentElement;
// Preliminary tests
div.setAttribute("className", "t");
div.innerHTML = " <link/><table></table><a href='/a' style='top:1px;float:left;opacity:.55;'>a</a><input type='checkbox'/>";
all = div.getElementsByTagName( "*" );
a = div.getElementsByTagName( "a" )[ 0 ];
// Can't get basic test support
if ( !all || !all.length || !a ) {
return {};
}
// First batch of supports tests
select = document.createElement( "select" );
opt = select.appendChild( document.createElement("option") );
input = div.getElementsByTagName( "input" )[ 0 ];
support = {
// Will be defined later
submitBubbles: true,
changeBubbles: true,
focusinBubbles: false,
deleteExpando: true,
noCloneEvent: true
};
// 3.1 如果浏览器再复制DOM元素时不复制事件监听函数,则测试项noCloneEvent为true
// 在IE6, IE7, IE8中,符合DOM元素时会连同事件监听函数一起复制,此时测试项noCloneEvent为false; 在IE9+和其他浏览器中,则不会复制事件,这时测试项noCloneEvent为true
// jQuery通过先复制绑定了事件的DOM元素,然后在副本元素上触发事件,并检测事件监听函数是否会执行,来测试测试项noCloneEvent.
// 在不支持方法addEventListner(type, listener, useCapture),但是支持方法attachEvent(ontype, listener)和fireEvent(ontype, event, canceled)的浏览器(即IE6, IE7, IE8)中,为div元素绑定onclick事件,并在副本元素上触发onclick事件
if ( !div.addEventListener && div.attachEvent && div.fireEvent ) {
div.attachEvent( "onclick", function() {
// Cloning a node shouldn't copy over any
// bound event handlers (IE does this)
support.noCloneEvent = false;
});
div.cloneNode( true ).fireEvent( "onclick" );
}
// Technique from Juriy Zaytsev
// http://perfectionkills.com/detecting-event-support-without-browser-sniffing/
// We only care about the case where non-standard event systems
// are used, namely in IE. Short-circuiting here helps us to
// avoid an eval call (in setAttribute) which can cause CSP
// to go haywire. See: https://developer.mozilla.org/en/Security/CSP
// 3.2 如果submit事件沿着DOM树向上冒泡,则测试项submitBubbles为true
// 在IE6,IE7,IE8中,submit事件不会向上冒泡,此时测试项submitBubbles为false,而在IE9+和其他浏览器则会向上冒泡,测试项submitBubbles为true
if ( div.attachEvent ) {
for( i in {
submit: 1,
change: 1,
focusin: 1
}) {
eventName = "on" + i;
isSupported = ( eventName in div );
if ( !isSupported ) {
div.setAttribute( eventName, "return;" );
isSupported = ( typeof div[ eventName ] === "function" );
}
support[ i + "Bubbles" ] = isSupported;
}
}
return support;
})();
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