一、jQuery.clean使用方法
jQuery.clean( elems, context, fragment, scripts );
二、思路分析
1、处理参数context，确保其为文档根节点document
2、处理参数elems数组(循环遍历数组)
　　2.1、elem为数字，转换为字符串
　　2.2、elem为非法值，跳出本次循环
　　2.3、elem为字符串
　　2.4、字符串不存在实体编号或html标签，则创建文本节点
　　2.5、字符串为实体编号或html标签
复制代码 代码如下:
创建一个div元素并插入到文档碎片中
 处理xhtml风格标签
 将elem包裹起来，并将包裹后的字符串作为div的innerHTML
 如果包裹深度大于1，只留下第一层包裹元素
 清除在ie6,7中空table标签自动加入的tbody
 将在ie9以下浏览器中剔除的开头空白字符串作为div元素的第一个文本子节点
 将elem重新赋值为div的子节点集合(nodeList对象),
 移除本次循环中文档碎片中的div，保持下一次循环中干净的div元素　　　　

2.3、如果elem为文本节点，则直接添加到要返回的ret数组中，否则将elem(nodeList对象)中的节点合并到数组
　　2.4、修复在ie6、7中type为radio，checkbox类型的节点的选中状态(checked)失效的bug
3、处理参数fragment
　　3.1、将ret中各节点添加到文档碎片fragment中
　　3.2、提取节点中的script子节点，并将其添加到ret数组中，添加的script位置为其原父元素位置后面
4、返回ret数组
三、源码注释分析
1、函数中用到的变量及函数
复制代码 代码如下:
var nodeNames = "abbr|article|aside|audio|bdi|canvas|data|datalist|details|figcaption|figure|footer|" +
         "header|hgroup|mark|meter|nav|output|progress|section|summary|time|video",
     wrapMap = {
         option: [ 1, "<select multiple='multiple'>", "</select>" ],
         legend: [ 1, "<fieldset>", "</fieldset>" ],
         thead: [ 1, "<table>", "</table>" ],
         tr: [ 2, "<table><tbody>", "</tbody></table>" ],
         td: [ 3, "<table><tbody><tr>", "</tr></tbody></table>" ],
         col: [ 2, "<table><tbody></tbody><colgroup>", "</colgroup></table>" ],
         area: [ 1, "<map>", "</map>" ],
         _default: [ 0, "", "" ]
     },
     rxhtmlTag = /<(?!area|br|col|embed|hr|img|input|link|meta|param)(([\w:]+)[^>]*)\/>/gi,
     rtagName = /<([\w:]+)/,
     rtbody = /<tbody/i,
     rhtml = /<|&#?\w+;/,
     rleadingWhitespace = /^\s+/,
     rcheckableType = /^(?:checkbox|radio)$/,
     rscriptType = /\/(java|ecma)script/i;
 // 设置复选框checkbox或单选框radio表单元素的默认选中状态
 function fixDefaultChecked( elem ) {
     if ( rcheckableType.test( elem.type ) ) {
         elem.defaultChecked = elem.checked;
     }
 }
 // 创建一个安全的文档碎片
 function createSafeFragment( document ) {
     var list = nodeNames.split( "|" ),
     safeFrag = document.createDocumentFragment(); // ie6,7,8浏览器把safeFrage作为HTMLDocument类型
     // 针对ie9以下浏览器
     if ( safeFrag.createElement ) {
         while ( list.length ) {
             safeFrag.createElement(
                 list.pop()
             );
         }
     }
     return safeFrag;
 }
 // 模拟ES5中Array的新功能
 // 该函数API：http://www.css88.com/jqapi-1.8/#p=jQuery.grep
 jQuery.extend({
     grep: function( elems, callback, inv ) {
         var retVal,
             ret = [],
             i = 0,
             length = elems.length;
         inv = !!inv;
         // Go through the array, only saving the items
         // that pass the validator function
         for ( ; i < length; i++ ) {
             retVal = !!callback( elems[ i ], i );
             if ( inv !== retVal ) {
                 ret.push( elems[ i ] );
             }
         }
         return ret;
     }             
 });

2、源码分析
复制代码 代码如下:
jQuery.extend({
     clean: function( elems, context, fragment, scripts ) {
         // 声明变量
         var i, j, elem, tag, wrap, depth, div, hasBody, tbody, len, handleScript, jsTags,
             safe = context === document && safeFragment,
             ret = [];
         // 确保变量context为文档根节点document
         if ( !context || typeof context.createDocumentFragment === "undefined" ) {
             context = document;
         }
         // Use the already-created safe fragment if context permits
         for ( i = 0; (elem = elems[i]) != null; i++ ) {
             // 如果elem为数字,则将其转换为字符串
             if ( typeof elem === "number" ) {
                 elem += "";
             }
             // 如果elem为undefined,跳出本次循环
             if ( !elem ) {
                 continue;
             }
             // Convert html string into DOM nodes
             // 转换数组项(字符串)为DOM节点
             if ( typeof elem === "string" ) {
                 // 如果不存在html实体编号或标签,则创建文本节点
                 if ( !rhtml.test( elem ) ) {
                     elem = context.createTextNode( elem );
                 }
                 // 处理是html标签字符串的数组项
                 else {
                     // Ensure a safe container in which to render the html
                     // safe为#document-fragment类型,在ie9以下浏览器中,safe为HTMLDocument类型节点,且nodeNames数组为空
                     safe = safe || createSafeFragment( context );
                     // 创建一个div元素并将其插入到文档碎片中
                     div = context.createElement("div");
                     safe.appendChild( div );
                     // Fix "XHTML"-style tags in all browsers
                     // 除了area,br,col,embed,hr,img,input,link,meta,param这些标签外,
                     // 将开始标签末尾加入斜杠的标签转换为开始和结束标签
                     elem = elem.replace(rxhtmlTag, "<$1></$2>");
                     // Go to html and back, then peel off extra wrappers
                     // 获取左边第一个标签元素
                     tag = ( rtagName.exec( elem ) || ["", ""] )[1].toLowerCase();
                     // 获取最外层元素的包裹元素,并将元素包裹在其中
                     wrap = wrapMap[ tag ] || wrapMap._default;
                     depth = wrap[0];
                     div.innerHTML = wrap[1] + elem + wrap[2];
                     // Move to the right depth
                     // 如果元素的包裹深度大于1,div重新赋值为元素最近的包裹元素(即:包含第一层包裹元素)
                     while ( depth-- ) {
                         div = div.lastChild;
                     }
                     // Remove IE's autoinserted <tbody> from table fragments
                     // 在IE6,7中,清除字符串中空table标签中自动加入的tbody标签(手动加入的除外)
                     if ( !jQuery.support.tbody ) {
                         // String was a <table>, *may* have spurious(伪造的) <tbody>
                         // 判断字符串中是否拥有空tbody标签
                         hasBody = rtbody.test(elem);
                         // 如果最外层标签为table且table中没有手动加入tbody
                         // 变量tbody为div.firstChild.childNodes(自动加入的tbody标签集合)
                         tbody = tag === "table" && !hasBody ?
                             div.firstChild && div.firstChild.childNodes :
                             // String was a bare <thead> or <tfoot>
                             // 如果字符串中仅有一个空thead或tfoot标签
                             // 变量tbody为div.childNodes(字符串中的thead和tfoot标签集合)
                             wrap[1] === "<table>" && !hasBody ?
                                 div.childNodes :
                                 [];
                         for ( j = tbody.length - 1; j >= 0 ; --j ) {
                             // 排除thead或tfoot标签
                             if ( jQuery.nodeName( tbody[ j ], "tbody" ) && !tbody[ j ].childNodes.length ) {
                                 // 清除空table标签中自动加入的tbody
                                 tbody[ j ].parentNode.removeChild( tbody[ j ] );
                             }
                         }
                     }
                     // IE completely kills leading whitespace when innerHTML is used
                     // 在ie9以下浏览器中,字符串以空白字符串开头,将空白字符串作为div元素的第一个文本子节点
                     if ( !jQuery.support.leadingWhitespace && rleadingWhitespace.test( elem ) ) {
                         div.insertBefore( context.createTextNode( rleadingWhitespace.exec(elem)[0] ), div.firstChild );
                     }
                     // 获取已经处理完毕的div子节点集合(nodeList对象)
                     elem = div.childNodes;
                     // Take out of fragment container (we need a fresh div each time)
                     // 在下一次循环处理字符串数组项前,清除处理创建过的div元素
                     div.parentNode.removeChild( div );
                 }
             }
             // 如果elem为DOM节点(文本节点)
             if ( elem.nodeType ) {
                 ret.push( elem );
             }
             // 将nodeList对象中节点合并到返回的数组中
             else {
                 jQuery.merge( ret, elem );
             }
         }
         // Fix #11356: Clear elements from safeFragment
         if ( div ) {
             elem = div = safe = null;
         }
         // Reset defaultChecked for any radios and checkboxes
         // about to be appended to the DOM in IE 6/7 (#8060)
         // 在ie6,7中,拥有checked属性的单选按钮,复选框在插入到其他标签后,选中状态会失效(下面代码修复该bug)
         if ( !jQuery.support.appendChecked ) {
             for ( i = 0; (elem = ret[i]) != null; i++ ) {
                 if ( jQuery.nodeName( elem, "input" ) ) {
                     fixDefaultChecked( elem );
                 } else if ( typeof elem.getElementsByTagName !== "undefined" ) {
                     jQuery.grep( elem.getElementsByTagName("input"), fixDefaultChecked );
                 }
             }
         }
         // Append elements to a provided document fragment
         // 将ret数组中的各DOM节点插入到提供的文档碎片中
         // 提取dom节点中的script节点，并添加到ret数组中，位置为其原父元素索引位置后
         if ( fragment ) {
             // Special handling of each script element
             handleScript = function( elem ) {
                 // Check if we consider it executable
                 // 如果elem元素不存在type属性或者type值为javascript或者为ecmascript
                 if ( !elem.type || rscriptType.test( elem.type ) ) {
                     // Detach the script and store it in the scripts array (if provided) or the fragment
                     // Return truthy to indicate that it has been handled
                     return scripts ?
                         scripts.push( elem.parentNode ? elem.parentNode.removeChild( elem ) : elem ) :
                         fragment.appendChild( elem );
                 }
             };
             for ( i = 0; (elem = ret[i]) != null; i++ ) {
                 // Check if we're done after handling an executable script
                 if ( !( jQuery.nodeName( elem, "script" ) && handleScript( elem ) ) ) {
                     // Append to fragment and handle embedded scripts
                     // 将elem元素添加到文档碎片中并处理嵌入的脚本(script标签元素)
                     fragment.appendChild( elem );
                     if ( typeof elem.getElementsByTagName !== "undefined" ) {
                         // handleScript alters the DOM, so use jQuery.merge to ensure snapshot iteration
                         jsTags = jQuery.grep( jQuery.merge( [], elem.getElementsByTagName("script") ), handleScript );
                         // Splice the scripts into ret after their former ancestor and advance our index beyond them
                         // 将script标签添加到数组，位置为其原父元素索引位置后
                         ret.splice.apply( ret, [i + 1, 0].concat( jsTags ) );
                         i += jsTags.length;
                     }
                 }
             }
         }
         return ret;
     }
 });