jquery源码——buildFragment

buildFragment是在context上，根据args创建一个div区域。核心部分是调用了clean部分。但是buildFragment添加了cache的部分。如果能cache的话，则直接返回创建好的。

具体情况加下：

jQuery.buildFragment = function( args, context, scripts ) { //传入的html代码段（好几段）,上下文，是否有scriptvar fragment, cacheable, cachehit,first = args[ 0 ];// Set context from what may come in as undefined or a jQuery collection or a nodecontext = context || document; //处理undefined的情况context = (context[0] || context).ownerDocument || context[0] || context; //处理jquery set 或者node的情况// Ensure that an attr object doesn't incorrectly stand in as a document object// Chrome and Firefox seem to allow this to occur and will throw exception// Fixes #8950if ( typeof context.createDocumentFragment === "undefined" ) { //createDocumentFragment常见用法是创建一个空的dom fragment，然后把elem append到fragment上，最后再把fragment append到doc 的DOM tree上context = document;}// Only cache "small" (1/2 KB) HTML strings that are associated with the main document// Cloning options loses the selected state, so don't cache them// IE 6 doesn't like it when you put <object> or <embed> elements in a fragment// Also, WebKit does not clone 'checked' attributes on cloneNode, so don't cache// Lastly, IE6,7,8 will not correctly reuse cached fragments that were created from unknown elems #10501if ( args.length === 1 && typeof first === "string" && first.length < 512 && context === document && //保证是小的代码段, 并且associated with main documentfirst.charAt(0) === "<" && !rnocache.test( first ) && //不是embed等情况(jQuery.support.checkClone || !rchecked.test( first )) && //允许clone并且没有checked属性(jQuery.support.html5Clone || !rnoshimcache.test( first )) ) { //允许h5特性，并且不是h5的那些新特性// Mark cacheable and look for a hitcacheable = true;fragment = jQuery.fragments[ first ]; //看看是不是有缓存的结果cachehit = fragment !== undefined;}if ( !fragment ) { //如果jQuery.fragments[]跪了，那么就创建一个空的 dom fragment，然后调用cleanfragment = context.createDocumentFragment();jQuery.clean( args, context, fragment, scripts );// Update the cache, but only store false// unless this is a second parsing of the same contentif ( cacheable ) {jQuery.fragments[ first ] = cachehit && fragment; //cache元素,cachehit的存在保证了只cache哪些能cache的元素}}return { fragment: fragment, cacheable: cacheable };};