jQuery源码-CSS样式相关部分-阿里云开发者社区

开发者社区> 开发与运维> 正文

jQuery源码-CSS样式相关部分

简介:

jquery版本:1.7.2

根据实际需要,对CSS部分无关代码进行适当删除,如有疑问,可参见jquery源码:http://code.jquery.com/jquery-1.7.2.js

因实际工作中暂时没有用到jquery,故对jquery了解很粗浅,文章可能有错漏之处,敬请见谅并指出

本文参考借鉴了nuysoft 的jquery源码分析系列,挺不错的系列文章,推荐下:

http://www.cnblogs.com/nuysoft/archive/2011/11/14/2248023.html

 


 

jquery里节点样式读取以及设置都是通过.css()这个方法来实现的,本章通过以下三个部分简单探究下jquery里这部分代码的实现

  1. 方法使用
  2. 源码概览
  3. 源码解析

一、方法使用

常见的有四种用法,包括一种读取样式三种设置样式:(详细可参见:http://api.jquery.com/css/

(1)读取样式:

.css(propertyName)  //用法1

 (2)设置演示:

.css(propertyName, value)  //用法2

.css(propertyName, function(index, oldValue))  //用法3

.css(map)  //用法4

首先看下面几个例子:



<div id="header"></div>
<ul id="list">
    <li></li> <li></li> <li></li>
</ul>


$('#header').css('height');  //读取样式值
$('#header').css('height', '10px');  //设置样式值
$('#header').css({height:'20px', 'width':'20px'});  //通过map方式设置多个属性
$('#list li').css('height', function(index, oldValue){ //通过传入function来设置样式,常用于集合操作
                                //index:为对应集合元素的索引,从0开始;而oldValue:元素原先样式
    return index*10+'px';  //返回值:节点最终设置的样式值
});

二、源码概览

主要代码:

  • jQuery.fn.css  //对外接口,样式读取、设置都通过它完成
  • jQuery.access  //jQuery.fn.css内部调用的,完成样式的读取、设置
  • jQuery.css  //读取节点样式(实际渲染后)
  • jQuery.style  //读取节点样式(内联样式)、设置节点样式
  • curCSS  //浏览器内置获取节点样式方法,为(1)支持标准的浏览器:getComputedStyle (2)IE系列:currentStyle

其他相关:

  • jQuery.cssHooks  //钩子函数,某些样式,如'height'、'width'等用到
  • jQuery.support  //浏览器对某些特性的支持,详情见下文
  • jQuery.swap  //节点隐藏等情况下,height、width等获取值不准,此时需利用此方法来获得准确值,详情见下文
  • jQuery.cssProps  //某些属性,在浏览器里有各自的别名,如float:IE里为styleFloat,遵守标准的浏览器里为cssFoat,详情见下文
  • jQuery.cssNumber  //某些属性,如z-index,为数值类型,不需要单位,详情见下文

相关正则:

    详情见下文

三、源码解析

主要代码:

  • jQuery.fn.css  //对外接口,样式读取、设置都通过它完成
    /**
     * @description 真正对外提供的接口,包括 读取/设置 dom节点样式 
     * @param 
     * @example 方式1:$('#header').css('height') ==> jQuery.css
     *          方式2:$('#header').css('height', '20px'),采用这种方式设置,只会对第一个元素进行样式设置 ==> jQuery.style
                方式3:$('ul#list li.item').css(attr, function(index,oldValue){}),最终在内部转换成 jQuery.style(attr, newValue)的形式 ==> jQuery.style
                方式4:$('#header').css({'height':'10px', 'width':'20px'}),最终在内部转换成$(node).style(attr, value)形式 ==> jQuery.style
     */
    jQuery.fn.css = function( name, value ) {
        //此处需要比较需要关心的是 function( elem, name, value ) 这个匿名方法
        //在jQuery.access经过各种判断检测后,最终就是调用这个匿名方法,遍历this,进行样式读取、设置
        //elem:设置/读取样式的节点
        //name:样式名
        //value:样式值
        return jQuery.access( this, function( elem, name, value ) {
            return value !== undefined ?
                jQuery.style( elem, name, value ) :    //设置样式,方式2、3、4的最终归宿,jQuery.style源码解析见下文
                jQuery.css( elem, name );    //读取样式,方法1的最终归宿,jQuery.css源码解析见下文
        }, name, value, arguments.length > 1 );    //arguments.length > 1,即value!=undefined,为设置样式
                                                //此处判断目的为:如设置样式,最后需返回elem,以实现链式调用,如$(node).css('height','10px').css('width','20px')
                                                //当采用$(node).css(map)方式设置,arguments.length == 1,按照此处逻辑判断,为读取样式
                                                //jQuery.access对这种情况进行了特殊处理,同样返回elem,个人觉得这里写法有点诡异
        
        //jQuery.access 定义如下,源码解析见下文;此处只是方便参照把定义拷贝了过来,源码里是没有下面这一句的
        //jQuery.access = function( elems, fn, key, value, chainable, emptyGet, pass ){}
        //在css样式设置这块,emptyGet、pass两个参数没用到,请直接忽视,
    };

  • jQuery.access  //jQuery.fn.css内部调用的,完成样式的读取、设置

备注:此方法在多处用到,此处只分析CSS相关部分,里面有部分参数、逻辑还有待了解



/**
 * @description 多功能函数,来自地狱的代码
 *              多处用到,包括 jQuery.fn.css, jQuery.fn.attr, jQuery.fn.prop,此处只分析CSS相关部分
 * @param {DOMObject} elems 读取/设置 样式的dom元素
 * @param {Function} fn 读取/设置 样式对应的方法(1)读取:jQuery.css(elem) (2)设置jQuery.style(elem,key,value)
 * @param {String} key 读取/设置 样式对应的属性,如.css('height'),则key === 'height'
 * @param {Boolean} chainable 是否需要返回jQuery对象实现链式调用
 * @emptyGet CSS样式部分貌似木有用到,暂忽略
 * @pass CSS样式部分貌似木有用到,暂忽略
*/
jQuery.access = function( elems, fn, key, value, chainable, emptyGet, pass ) {
    var exec,
        bulk = key == null,    //key==null,表示key为null或者undefined
        i = 0,    //多么糟糕的变量啊!!又做index索引,又做对象的键值
        length = elems.length;

    // Sets many values
    if ( key && typeof key === "object" ) {    //设置样式,对应jQuery.fn.css 方式4,如:$('#header').css({'height':'10px', 'width':'20px'})
        //通过遍历哈希表方式,逐个设置节点样式
        //此时key形式为:{'height':'10px', 'width':'20px'},key这变量名相当有迷惑性
        for ( i in key ) {
            jQuery.access( elems, fn, i, key[i], 1, emptyGet, value );    //逐个设置样式,此处value==undefined
        }
        chainable = 1;    //chainable = 1 ,表示此处设置样式

    // Sets one value
    } else if ( value !== undefined ) {    //设置样式,如方式3:$('ul#list li.item').css('height', function(index,node){})
                                                    //方式2:$('#header').css('height', '20px')
        // Optionally, function values get executed if exec is true
        exec = pass === undefined && jQuery.isFunction( value );    //exec == true,则表示采用.css( property, function(index, oldValue) )方式设置样式

        if ( bulk ) {    //@todo:目前还没想到神马情况下会走到这个分支里,有可能CSS样式设置里不会出现,待进一步考察
            // Bulk operations only iterate when executing function values
            if ( exec ) {
                exec = fn;
                fn = function( elem, key, value ) {
                    return exec.call( jQuery( elem ), value );
                };

            // Otherwise they run against the entire set
            } else {
                fn.call( elems, value );
                fn = null;
            }
        }

        if ( fn ) {    
            for (; i < length; i++ ) {    //遍历集合里的元素
                //value.call( elems[i], i, fn( elems[i], key ) )返回节点设置之前的的样式
                //value ==> function(index, oldValue),i对应index, fn( elems[i], key )对应oldValue, fn为 jQuery.css
                //exec值参见上文
                fn( elems[i], key, exec ? value.call( elems[i], i, fn( elems[i], key ) ) : value, pass );
            }
        }

        chainable = 1;
    }
    
    return chainable ?    //chainable == 1,表示设置样式,返回设置样式的元素,实现链式调用
        // 设置样式,返回元素
        elems :

        // 获取样式
        bulk ?    //bulk值参见上文
            fn.call( elems ) :    
            length ? fn( elems[0], key ) : emptyGet;    //此时fn对应 jQuery.css
                                                        //当elems为集合元素时,返回集合里第一个元素key对应的样式值
                                 //此处的返回值为access的返回值,也即.css(propertyName)的返回值
}
  • jQuery.css  //读取节点样式(实际渲染后)

/**
     * @description 读取 dom 实际渲染的样式值
     * @param {DOMObject} elem 获取样式的dom节点
     * @param {String} name 样式名
     * @param extra 
    */
    css: function( elem, name, extra ) {
        var ret, hooks;

        // Make sure that we're working with the right name
        name = jQuery.camelCase( name );    //转成驼峰形式,如margin-left --> marginLeft
        hooks = jQuery.cssHooks[ name ];    //某些特定的属性有对应的get、set方法,如'height'、'width'、'opacity'等
        name = jQuery.cssProps[ name ] || name;    //对某些特殊属性,如float进行修正

        // cssFloat needs a special treatment
        if ( name === "cssFloat" ) {    //兼容标准的浏览器如chrome,用$(node).css('float')或$(node).css('cssFloat')
            name = "float";
        }

        // If a hook was provided get the computed value from there
        //如果有对应的hook对象,且该对象有get方法,则调用hooks[name].get 来获取样式值
        if ( hooks && "get" in hooks && (ret = hooks.get( elem, true, extra )) !== undefined ) {
            return ret;
        // Otherwise, if a way to get the computed value exists, use that
        } else if ( curCSS ) {    //否则,通过curCSS方法来获取实际渲染后的样式值,curCSS定义见curCSS部分说明
            return curCSS( elem, name );
        }
    },

  • jQuery.style  //读取节点样式(内联样式)、设置节点样式

// Get and set the style property on a DOM Node
    /**
     * @description 读取/设置 dom 节点样式
     * @param {DOMObject} elem dom节点
     * @param {String} name 属性值
     * @param {String|Number} value 样式值
     * @note 当获取样式值时,返回的是内联样式值,而非浏览器实际渲染后的值
    */
    style: function( elem, name, value, extra ) {
        // Don't set styles on text and comment nodes
        //elem.nodeType ==> 3:文本,8:注释,此处过滤文本、注释节点
        //elem为document,则document.style == undefined,过滤无法设置属性的节点
        if ( !elem || elem.nodeType === 3 || elem.nodeType === 8 || !elem.style ) {
            return;
        }

        // Make sure that we're working with the right name
        var ret, type, origName = jQuery.camelCase( name ),    //返回驼峰命名形式的属性名
            style = elem.style, hooks = jQuery.cssHooks[ origName ];

        name = jQuery.cssProps[ origName ] || origName;    //float返回cssFloat或styleFloat(目前就只对这个属性进行特殊处理)

        // Check if we're setting a value
        if ( value !== undefined ) {
            type = typeof value;

            // convert relative number strings (+= or -=) to relative numbers. #7345
            //采用相对值进行设置,如$(node).css('height','+=10px')
            //ret = rrelNum.exec( value ),如采用相对值进行设置,则:
            //ret[1]:+/-
            //ret[2]:相对值的大小
            if ( type === "string" && (ret = rrelNum.exec( value )) ) {
                value = ( +( ret[1] + 1) * +ret[2] ) + parseFloat( jQuery.css( elem, name ) );    //将相对值与原来的属性值进行运算,获得实际设置的值
                // Fixes bug #9237
                type = "number";
            }

            // Make sure that NaN and null values aren't set. See: #7116
            //如果设置的值为 null 或者 NaN,则不设置,直接返回
            if ( value == null || type === "number" && isNaN( value ) ) {
                return;
            }

            // If a number was passed in, add 'px' to the (except for certain CSS properties)
            //如果传进来的值是number类型,如.css('height',10),则给10加上单位px
            if ( type === "number" && !jQuery.cssNumber[ origName ] ) {
                value += "px";
            }

            // If a hook was provided, use that value, otherwise just set the specified value
            //如果该属性存在对应钩子对象,且该对象有set方法,则调用刚set方法设置样式值
            if ( !hooks || !("set" in hooks) || (value = hooks.set( elem, value )) !== undefined ) {
                // Wrapped to prevent IE from throwing errors when 'invalid' values are provided
                // Fixes bug #5509
                try {
                    style[ name ] = value;
                } catch(e) {}
            }

        } else {
            //如果value没有提供,jQuery.css返回内联样式值
            // If a hook was provided get the non-computed value from there
            if ( hooks && "get" in hooks && (ret = hooks.get( elem, false, extra )) !== undefined ) {
                return ret;
            }
            // Otherwise just get the value from the style object
            return style[ name ];
        }
    },

  • curCSS  //浏览器内置获取节点样式方法,为(1)遵守支持标准的浏览器:getComputedStyle (2)IE系列:currentStyle

//处理遵守W3C标准的浏览器
//在浏览器里,document.defaultView返回与document相关的window对象,如果不存在,则返回null
//IE9以下版本的IE系列不支持defaultView
//其实可以直接window.getComputedStyle,除了一种情况,见:https://developer.mozilla.org/en-US/docs/DOM/window.getComputedStyle
//getComputedStyle() gives the final used values of all the CSS properties of an element.
//比如样式表里设置font-size:12px,内联样式设置font-size:20px,返回的是20px
if ( document.defaultView && document.defaultView.getComputedStyle ) {    //兼容标准的浏览器
    getComputedStyle = function( elem, name ) {
        var ret, defaultView, computedStyle, width,
            style = elem.style;
        name = name.replace( rupper, "-$1" ).toLowerCase();    //将属性名转换成margin-left这种带连字符的形式
                                                            //rupper定义:rupper = /([A-Z]|^ms)/g
        if ( (defaultView = elem.ownerDocument.defaultView) &&
                (computedStyle = defaultView.getComputedStyle( elem, null )) ) {    //ownerDocument 可返回某元素的根元素,定义见:https://developer.mozilla.org/en-US/docs/DOM/Node.ownerDocument
                                                                                    //getComputedStyle,返回计算后的样式值,定义见:https://developer.mozilla.org/en-US/docs/DOM/window.getComputedStyle
                                                                                    //关于getComputedStyle与computed value、used value的关系:https://developer.mozilla.org/en-US/docs/CSS/computed_value
            ret = computedStyle.getPropertyValue( name );    //
            if ( ret === "" && !jQuery.contains( elem.ownerDocument.documentElement, elem ) ) {    //这句的作用??
                ret = jQuery.style( elem, name );
            }
            //document.documentElement返回文档的的根节点,比如html文档的<html>元素
        }

        // A tribute to the "awesome hack by Dean Edwards"
        // WebKit uses "computed value (percentage if specified)" instead of "used value" for margins
        // which is against the CSSOM draft spec: http://dev.w3.org/csswg/cssom/#resolved-values
        //jQuery.support.pixelMargin:是否支持margin返回的结果是px为单位(webkit里面,如果设置了百分值,则返回百分值)??
        //经chrome测试,jQuery.support.pixelMargin === true
        if ( !jQuery.support.pixelMargin && computedStyle && rmargin.test( name ) && rnumnonpx.test( ret ) ) {
            width = style.width;
            style.width = ret;
            ret = computedStyle.width;
            style.width = width;
        }

        return ret;
    };
}

//IE浏览器,此处留坑待填
if ( document.documentElement.currentStyle ) {    //currentStyle:IE浏览器特有的属性
    currentStyle = function( elem, name ) {
        var left, rsLeft, uncomputed,
            ret = elem.currentStyle && elem.currentStyle[ name ],
            style = elem.style;

        // Avoid setting ret to empty string here
        // so we don't default to auto
        if ( ret == null && style && (uncomputed = style[ name ]) ) {
            ret = uncomputed;
        }

        // From the awesome hack by Dean Edwards
        // http://erik.eae.net/archives/2007/07/27/18.54.15/#comment-102291

        // If we're not dealing with a regular pixel number
        // but a number that has a weird ending, we need to convert it to pixels
        if ( rnumnonpx.test( ret ) ) {    //rnumnonpx定义:rnumnonpx = /^-?(?:\d*\.)?\d+(?!px)[^\d\s]+$/i

            // Remember the original values
            left = style.left;
            rsLeft = elem.runtimeStyle && elem.runtimeStyle.left;

            // Put in the new values to get a computed value out
            if ( rsLeft ) {
                elem.runtimeStyle.left = elem.currentStyle.left;
            }
            style.left = name === "fontSize" ? "1em" : ret;
            ret = style.pixelLeft + "px";

            // Revert the changed values
            style.left = left;
            if ( rsLeft ) {
                elem.runtimeStyle.left = rsLeft;
            }
        }

        return ret === "" ? "auto" : ret;
    };
}

curCSS = getComputedStyle || currentStyle;

其他相关:

  • jQuery.cssHooks  //钩子函数,某些样式,如'height'、'width'等用到

jQuery.extend({
    // Add in style property hooks for overriding the default
    // behavior of getting and setting a style property
    //钩子方法,对一些特殊的属性,需要有特殊的样式读取(get)、设置(set)方法
    cssHooks: {
        //@cssHooks1:透明度
        opacity: {
            get: function( elem, computed ) {
                if ( computed ) {
                    // We should always get a number back from opacity
                    var ret = curCSS( elem, "opacity" );
                    return ret === "" ? "1" : ret;

                } else {
                    return elem.style.opacity;
                }
            }
        }
    }
});

//@cssHooks3:透明度
if ( !jQuery.support.opacity ) {    //如果不支持style.opacity,关于support下文有讲到,暂时从字面上理解即可
    jQuery.cssHooks.opacity = {
        get: function( elem, computed ) {
            // IE uses filters for opacity
            return ropacity.test( (computed && elem.currentStyle ? elem.currentStyle.filter : elem.style.filter) || "" ) ?    //IE:是否存在filter:alpha(opacity=30)的样式设置
                ( parseFloat( RegExp.$1 ) / 100 ) + "" :    //存在:将opacity转换成小数点形式(与遵守标准的浏览器保持一致)
                computed ? "1" : "";    //不存在:未设置opacity,视为全部透明,即1
        },

        set: function( elem, value ) {
            var style = elem.style,
                currentStyle = elem.currentStyle,
                opacity = jQuery.isNumeric( value ) ? "alpha(opacity=" + value * 100 + ")" : "",    //为IE、非IE保持一致,需要乘以100
                filter = currentStyle && currentStyle.filter || style.filter || "";

            // IE has trouble with opacity if it does not have layout
            // Force it by setting the zoom level
            style.zoom = 1;    //此处为解决IE bug,表示还不知道有这么个bug存在于人世间,重构的兄弟们辛苦了

            // if setting opacity to 1, and no other filters exist - attempt to remove filter attribute #6652
            if ( value >= 1 && jQuery.trim( filter.replace( ralpha, "" ) ) === "" ) {

                // Setting style.filter to null, "" & " " still leave "filter:" in the cssText
                // if "filter:" is present at all, clearType is disabled, we want to avoid this
                // style.removeAttribute is IE Only, but so apparently is this code path...
                style.removeAttribute( "filter" );

                // if there there is no filter style applied in a css rule, we are done
                if ( currentStyle && !currentStyle.filter ) {
                    return;
                }
            }

            // otherwise, set new filter values
            style.filter = ralpha.test( filter ) ?
                filter.replace( ralpha, opacity ) :
                filter + " " + opacity;
        }
    };
}

//@cssHooks4:marginRight(右外边距)
//据说是为了处理神bug存在的,就不伤害自己脑细胞了,了解下即可
jQuery(function() {
    // This hook cannot be added until DOM ready because the support test
    // for it is not run until after DOM ready
    if ( !jQuery.support.reliableMarginRight ) {
        jQuery.cssHooks.marginRight = {
            get: function( elem, computed ) {
                // WebKit Bug 13343 - getComputedStyle returns wrong value for margin-right
                // Work around by temporarily setting element display to inline-block
                return jQuery.swap( elem, { "display": "inline-block" }, function() {
                    if ( computed ) {
                        return curCSS( elem, "margin-right" );
                    } else {
                        return elem.style.marginRight;
                    }
                });
            }
        };
    }
});

// These hooks are used by animate to expand properties
//@cssHooks5:待填坑
jQuery.each({
    margin: "",
    padding: "",
    border: "Width"
}, function( prefix, suffix ) {

    jQuery.cssHooks[ prefix + suffix ] = {
        expand: function( value ) {
            var i,

                // assumes a single number if not a string
                parts = typeof value === "string" ? value.split(" ") : [ value ],
                expanded = {};

            for ( i = 0; i < 4; i++ ) {
                expanded[ prefix + cssExpand[ i ] + suffix ] =
                    parts[ i ] || parts[ i - 2 ] || parts[ 0 ];
            }

            return expanded;
        }
    };
});

//@cssHooks2用到
function getWidthOrHeight( elem, name, extra ) {

    // Start with offset property
    var val = name === "width" ? elem.offsetWidth : elem.offsetHeight,
        i = name === "width" ? 1 : 0,
        len = 4;

    if ( val > 0 ) {    //此处作用,减去paddingTopWidth、paddingBottomWidth、borderTopWidth、borderBottomWidth,要不要这么隐晦啊啊!!!
        if ( extra !== "border" ) {
            for ( ; i < len; i += 2 ) {
                if ( !extra ) {
                    val -= parseFloat( jQuery.css( elem, "padding" + cssExpand[ i ] ) ) || 0;
                }
                if ( extra === "margin" ) {
                    val += parseFloat( jQuery.css( elem, extra + cssExpand[ i ] ) ) || 0;
                } else {
                    val -= parseFloat( jQuery.css( elem, "border" + cssExpand[ i ] + "Width" ) ) || 0;
                }
            }
        }

        return val + "px";
    }

    // Fall back to computed then uncomputed css if necessary
    val = curCSS( elem, name );
    if ( val < 0 || val == null ) {    //会有小于0的情况吗???
        val = elem.style[ name ];
    }

    // Computed unit is not pixels. Stop here and return.
    if ( rnumnonpx.test(val) ) {    //val单位非px
        return val;
    }

    // Normalize "", auto, and prepare for extra
    val = parseFloat( val ) || 0;

    // Add padding, border, margin
    //目测:在getClentHeight、getClientWidth等处可以用到
    if ( extra ) {
        for ( ; i < len; i += 2 ) {
            val += parseFloat( jQuery.css( elem, "padding" + cssExpand[ i ] ) ) || 0;
            if ( extra !== "padding" ) {
                val += parseFloat( jQuery.css( elem, "border" + cssExpand[ i ] + "Width" ) ) || 0;
            }
            if ( extra === "margin" ) {
                val += parseFloat( jQuery.css( elem, extra + cssExpand[ i ]) ) || 0;
            }
        }
    }

    return val + "px";
}

  • jQuery.support  //浏览器对某些特性的支持,详情见下文

//各种测试是否支持某些属性
//仅将CSS相关部分挑出来,完整的support方法包注释200++行,有兴趣可以看下源码
jQuery.support = (function(){
    var marginDiv,
        div = document.createElement( "div" );
    div.innerHTML = "   <link/><table></table><a href='/a' style='top:1px;float:left;opacity:.55;'>a</a><input type='checkbox'/>";    
    
    var a = div.getElementsByTagName( "a" )[ 0 ];
    
    var support = {
        // 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 ),    //是否支持opacity==>IE6/7/8采用filter来实现(半)透明效果,
        
        // Verify style float existence
        // (IE uses styleFloat instead of cssFloat)
        cssFloat: !!a.style.cssFloat,    //(1)IE:node.style.styleFloat(2)chrome等:node.style.cssFloat
        
        reliableMarginRight: true,        //解决webkit的bug:getComputedStyle返回错误的margin-right值
                                        //解决方案:暂时将节点的display属性设为inline-block
        pixelMargin: true,    //是否支持margin返回的结果是px为单位(webkit里面,如果设置了百分值,则返回百分值),测试了下chrome下是ok的    
    };
    
    // 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 ) {    //jQuery.support.reliableMarginRight
        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 ( window.getComputedStyle ) {    //jQuery.support.pixelMargin
        div.style.marginTop = "1%";
        support.pixelMargin = ( window.getComputedStyle( div, null ) || { marginTop: 0 } ).marginTop !== "1%";
    }    
    
    return support;
})();

  • jQuery.swap  //节点隐藏等情况下,height、width等获取值不准,此时需利用此方法来获得准确值

jQuery.extend({
    // A method for quickly swapping in/out CSS properties to get correct calculations
    //将offsetHeight、offsetWidth为0的元素快速修改样式,获得需要的值后,再改回去
    //options:{display:'block',position:'absolute',visibility:'hidden'}
    /**
     * @description 将offsetHeight、offsetWidth为0(可能因display=none等原因导致)的元素快速修改样式,获得浏览器实际渲染的值后,再改回去
     * @param {DOMObject} elem dom节点
     * @param {Object} options {display:'block',position:'absolute',visibility:'hidden'}
     * @param {Function} callback 回调方法,如获取修改后的dom节点的宽、高等
    */
    swap: function( elem, options, callback ) {
        var old = {},
            ret, name;
 
        // Remember the old values, and insert the new ones
        for ( name in options ) {   //先将dom元素设置为display=block;position=absolute;visibility=hidden;
            old[ name ] = elem.style[ name ];
            elem.style[ name ] = options[ name ];
        }
 
        ret = callback.call( elem );
 
        // Revert the old values
        for ( name in options ) {   //将改变的display、position、visibiliby设置回去
            elem.style[ name ] = old[ name ];
        }
 
        return ret;
    }
});

  • jQuery.cssProps  //某些属性,在浏览器里有各自的别名,如float:IE里为styleFloat,遵守标准的浏览器里为cssFoat

jQuery.extend({
    // Add in properties whose names you wish to fix before
    // setting or getting the value
    //此处的属性名需要特殊处理,如float,在IE里为node.style.styleFloat,支持标准的浏览器里为node.style.cssFloat
    cssProps: {
        // normalize float css property
        "float": jQuery.support.cssFloat ? "cssFloat" : "styleFloat"
    }
});
  • jQuery.cssNumber  //某些属性,如z-index,为数值类型,不需要单位

jQuery.extend({
    // Exclude the following css properties to add px
    //排除一下css属性,无需加px,此处有些疑问,如lineHeight,需再研究下。
    cssNumber: {
        "fillOpacity": true,
        "fontWeight": true,
        "lineHeight": true,
        "opacity": true,
        "orphans": true,
        "widows": true,
        "zIndex": true,
        "zoom": true
    }
});

相关正则等:

var ralpha = /alpha\([^)]*\)/i,    //匹配如:alpha(opacity=20)
    ropacity = /opacity=([^)]*)/,    //匹配如:filter:alpha(opacity=20)等形式
    // fixed for IE9, see #8346
    rupper = /([A-Z]|^ms)/g,    //此处暂不明,但觉厉,需再探究下
    rnum = /^[\-+]?(?:\d*\.)?\d+$/i,    //匹配数字(包括浮点),如(+/-)1、(+/-)0.1、(+/-).1、(+/-)1.1
    rnumnonpx = /^-?(?:\d*\.)?\d+(?!px)[^\d\s]+$/i,    //非px值,如'10em'、'10%'等
    rrelNum = /^([\-+])=([\-+.\de]+)/,    //设置属性支持相对写法,如$('#header').css('height', '+=10px')等。。
    rmargin = /^margin/,    //属性是否为margin开头的,如margin-left、margin-top等

    cssShow = { position: "absolute", visibility: "hidden", display: "block" },    //对于offsetHeight或offsetWidth为0的元素

    // order is important!
    cssExpand = [ "Top", "Right", "Bottom", "Left" ],    //计算宽、高用到

    curCSS,    //最终只是把getComputedStyle或currentStyle方法其中之一赋给curCss

    getComputedStyle,    //遵守标准的浏览器获取css样式的方法
    currentStyle;    //IE浏览器获取css样式的方法




版权声明:本文内容由阿里云实名注册用户自发贡献,版权归原作者所有,阿里云开发者社区不拥有其著作权,亦不承担相应法律责任。具体规则请查看《阿里云开发者社区用户服务协议》和《阿里云开发者社区知识产权保护指引》。如果您发现本社区中有涉嫌抄袭的内容,填写侵权投诉表单进行举报,一经查实,本社区将立刻删除涉嫌侵权内容。

分享:
开发与运维
使用钉钉扫一扫加入圈子
+ 订阅

集结各类场景实战经验,助你开发运维畅行无忧

其他文章