jQuery中的support对象

jQuery.support是为了替换jQuery.browser而来。

browser带着版本号的信息，浏览器有更新（IE10）时，很多以前的判断条件都不生效，所以更改为对特性的支持，以此来区分浏览器的不同。

(function( jQuery ) {  
  
jQuery.support = (function() {  
  
    var support,  
        all,  
        a,  
        select,  
        opt,  
        input,  
        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  
    // 如果不支持getElementsByTagName()方法，则支持返回空对象，  
    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 = {  
        // IE strips leading whitespace when .innerHTML is used  
        // IE下.innerHTML将左右空格去除，得到的nodeType === 1  
        leadingWhitespace: ( div.firstChild.nodeType === 3 ),  
  
        // Make sure that tbody elements aren't automatically inserted  
        // IE will insert them into empty tables  
        // IE往空的table添加tbody标签  
        tbody: !div.getElementsByTagName("tbody").length,  
  
        // Make sure that link elements get serialized correctly by innerHTML  
        // This requires a wrapper element in IE  
        // 在IE下查找link的长度为0,需要将link内容包含在dom元素中  
        htmlSerialize: !!div.getElementsByTagName("link").length,  
  
        // Get the style information from getAttribute  
        // (IE uses .cssText instead)  
        // IE中使用a.getAttribute("style").cssText来获取style中的文本信息  
        style: /top/.test( a.getAttribute("style") ),  
  
        // Make sure that URLs aren't manipulated  
        // (IE normalizes it by default)  
        // IE中a的getAttribute方法默认将href属性转义成绝对路径，网上有个网页分析得非常得当  
        hrefNormalized: ( a.getAttribute("href") === "/a" ),  
  
        // Make sure that element opacity exists  
        // (IE uses filter instead)  
        // Use a regex to work around a WebKit issue. See #5145  
        opacity: /^0.55/.test( a.style.opacity ),  
  
        // Verify style float existence  
        // (IE uses styleFloat instead of cssFloat)  
        // 浏览器的差异  
        cssFloat: !!a.style.cssFloat,  
  
        // Make sure that if no value is specified for a checkbox  
        // that it defaults to "on".  
        // (WebKit defaults to "" instead)  
        // 在chrome中 defaults为on，是否jQuery中有存在问题  
        checkOn: ( input.value === "on" ),  
  
        // Make sure that a selected-by-default option has a working selected property.  
        // (WebKit defaults to false instead of true, IE too, if it's in an optgroup)  
        optSelected: opt.selected,  
  
        // Test setAttribute on camelCase class. If it works, we need attrFixes when doing get/setAttribute (ie6/7)  
        // 测试是否支持驼峰式的样式，如果支持，在IE6和IE7的get/setAttribute方法中采用attrFixes修正  
        getSetAttribute: div.className !== "t",  
  
        // Tests for enctype support on a form(#6743)  
        // 测试form是否支持enctype  
        enctype: !!document.createElement("form").enctype,  
  
        // Makes sure cloning an html5 element does not cause problems  
        // Where outerHTML is undefined, this still works  
        // 确保克隆一个html5元素时不会导致问题  
        html5Clone: document.createElement("nav").cloneNode( true ).outerHTML !== "<:nav></:nav>",  
  
        // 所以，现在我们不需要这些  
        // Will be defined later  
        submitBubbles: true,  
        changeBubbles: true,  
        focusinBubbles: false,  
        deleteExpando: true,  
        noCloneEvent: true,  
        inlineBlockNeedsLayout: false,  
        shrinkWrapBlocks: false,  
        reliableMarginRight: true,  
        pixelMargin: true  
    };  
  
    // jQuery.boxModel DEPRECATED in 1.3, use jQuery.support.boxModel instead  
    jQuery.boxModel = support.boxModel = (document.compatMode === "CSS1Compat");  
  
    // Make sure checked status is properly cloned  
    input.checked = true;  
    support.noCloneChecked = input.cloneNode( true ).checked;  
  
    // Make sure that the options inside disabled selects aren't marked as disabled  
    // (WebKit marks them as disabled)  
    select.disabled = true;  
    support.optDisabled = !opt.disabled;  
  
    // Test to see if it's possible to delete an expando from an element  
    // Fails in Internet Explorer  
    try {  
        delete div.test;  
    } catch( e ) {  
        support.deleteExpando = false;  
    }  
  
    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" );  
    }  
  
    // Check if a radio maintains its value  
    // after being appended to the DOM  
    // 加入一个radio后，查看是否仍保留它的值  
    input = document.createElement("input");  
    input.value = "t";  
    input.setAttribute("type", "radio");  
    support.radioValue = input.value === "t";  
  
    input.setAttribute("checked", "checked");  
  
    // #11217 - WebKit loses check when the name is after the checked attribute  
    input.setAttribute( "name", "t" );  
  
    div.appendChild( input );  
    fragment = document.createDocumentFragment();  
    fragment.appendChild( div.lastChild );  
  
    // WebKit doesn't clone checked state correctly in fragments  
    // WebKit克隆时不支持checked状态  
    support.checkClone = fragment.cloneNode( true ).cloneNode( true ).lastChild.checked;  
  
    // Check if a disconnected checkbox will retain its checked  
    // value of true after appended to the DOM (IE6/7)  
    support.appendChecked = input.checked;  
  
    fragment.removeChild( input );  
    fragment.appendChild( div );  
  
    // 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  
    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;  
        }  
    }  
  
    fragment.removeChild( div );  
  
    // Null elements to avoid leaks in IE  
    fragment = select = opt = div = input = null;  
  
    // Run tests that need a body at doc ready  
    jQuery(function() {  
        var container, outer, inner, table, td, offsetSupport,  
            marginDiv, conMarginTop, style, html, positionTopLeftWidthHeight,  
            paddingMarginBorderVisibility, paddingMarginBorder,  
            body = document.getElementsByTagName("body")[0];  
  
        if ( !body ) {  
            // Return for frameset docs that don't have a body  
            return;  
        }  
  
        conMarginTop = 1;  
        paddingMarginBorder = "padding:0;margin:0;border:";  
        positionTopLeftWidthHeight = "position:absolute;top:0;left:0;width:1px;height:1px;";  
        paddingMarginBorderVisibility = paddingMarginBorder + "0;visibility:hidden;";  
        style = "style='" + positionTopLeftWidthHeight + paddingMarginBorder + "5px solid #000;";  
        html = "<div " + style + "display:block;'><div style='" + paddingMarginBorder + "0;display:block;overflow:hidden;'></div></div>" +  
            "<table " + style + "' cellpadding='0' cellspacing='0'>" +  
            "<tr><td></td></tr></table>";  
  
        container = document.createElement("div");  
        container.style.cssText = paddingMarginBorderVisibility + "width:0;height:0;position:static;top:0;margin-top:" + conMarginTop + "px";  
        body.insertBefore( container, body.firstChild );  
  
        // Construct the test element  
        div = document.createElement("div");  
        container.appendChild( div );  
  
        // Check if table cells still have offsetWidth/Height when they are set  
        // to display:none and there are still other visible table cells in a  
        // table row; if so, offsetWidth/Height are not reliable for use when  
        // determining if an element has been hidden directly using  
        // display:none (it is still safe to use offsets if a parent element is  
        // hidden; don safety goggles and see bug #4512 for more information).  
        // (only IE 8 fails this test)  
        div.innerHTML = "<table><tr><td style='" + paddingMarginBorder + "0;display:none'></td><td>t</td></tr></table>";  
        tds = div.getElementsByTagName( "td" );  
        isSupported = ( tds[ 0 ].offsetHeight === 0 );  
  
        tds[ 0 ].style.display = "";  
        tds[ 1 ].style.display = "none";  
  
        // Check if empty table cells still have offsetWidth/Height  
        // (IE <= 8 fail this test)  
        support.reliableHiddenOffsets = isSupported && ( tds[ 0 ].offsetHeight === 0 );  
  
        // Check if div with explicit width and no margin-right incorrectly  
        // gets computed margin-right based on width of container. For more  
        // info see bug #3333  
        // Fails in WebKit before Feb 2011 nightlies  
        // WebKit Bug 13343 - getComputedStyle returns wrong value for margin-right  
        if ( window.getComputedStyle ) {  
            div.innerHTML = "";  
            marginDiv = document.createElement( "div" );  
            marginDiv.style.width = "0";  
            marginDiv.style.marginRight = "0";  
            div.style.width = "2px";  
            div.appendChild( marginDiv );  
            support.reliableMarginRight =  
                ( parseInt( ( window.getComputedStyle( marginDiv, null ) || { marginRight: 0 } ).marginRight, 10 ) || 0 ) === 0;  
        }  
  
        if ( typeof div.style.zoom !== "undefined" ) {  
            // Check if natively block-level elements act like inline-block  
            // elements when setting their display to 'inline' and giving  
            // them layout  
            // (IE < 8 does this)  
            div.innerHTML = "";  
            div.style.width = div.style.padding = "1px";  
            div.style.border = 0;  
            div.style.overflow = "hidden";  
            div.style.display = "inline";  
            div.style.zoom = 1;  
            support.inlineBlockNeedsLayout = ( div.offsetWidth === 3 );  
  
            // Check if elements with layout shrink-wrap their children  
            // (IE 6 does this)  
            div.style.display = "block";  
            div.style.overflow = "visible";  
            div.innerHTML = "<div style='width:5px;'></div>";  
            support.shrinkWrapBlocks = ( div.offsetWidth !== 3 );  
        }  
  
        div.style.cssText = positionTopLeftWidthHeight + paddingMarginBorderVisibility;  
        div.innerHTML = html;  
  
        outer = div.firstChild;  
        inner = outer.firstChild;  
        td = outer.nextSibling.firstChild.firstChild;  
  
        offsetSupport = {  
            doesNotAddBorder: ( inner.offsetTop !== 5 ),  
            doesAddBorderForTableAndCells: ( td.offsetTop === 5 )  
        };  
  
        inner.style.position = "fixed";  
        inner.style.top = "20px";  
  
        // safari subtracts parent border width here which is 5px  
        offsetSupport.fixedPosition = ( inner.offsetTop === 20 || inner.offsetTop === 15 );  
        inner.style.position = inner.style.top = "";  
  
        outer.style.overflow = "hidden";  
        outer.style.position = "relative";  
  
        offsetSupport.subtractsBorderForOverflowNotVisible = ( inner.offsetTop === -5 );  
        offsetSupport.doesNotIncludeMarginInBodyOffset = ( body.offsetTop !== conMarginTop );  
  
        if ( window.getComputedStyle ) {  
            div.style.marginTop = "1%";  
            support.pixelMargin = ( window.getComputedStyle( div, null ) || { marginTop: 0 } ).marginTop !== "1%";  
        }  
  
        if ( typeof container.style.zoom !== "undefined" ) {  
            container.style.zoom = 1;  
        }  
  
        body.removeChild( container );  
        marginDiv = div = container = null;  
  
        jQuery.extend( support, offsetSupport );  
    });  
  
    return support;  
})();  
  
})( jQuery );