//整个extend函数代表着如何寻找过来的参数(可以是任何对象【数组也是对象】),返回需要的对象。在javascirpt中extend理论之一是合并或复制对象。那么如何<pre name="code" class="javascript">复制<span style="font-family: Arial, Helvetica, sans-serif;">呢?基本的理论在我的http://blog.csdn.net/luozhonghua2014/article/details/45790867文章中。jquery源码真实体现了这些理论。读者朋友研究源码,建议除了基本理论外,建议写个插件或直接用jquery的方法去debugger;这样很容易看到jquery如何工作及优点。编写优于jquery的插件或补充是程序员的前端基本功,也是走向高级架构师的入点。</span>
jQuery.extend = jQuery.fn.extend = function() { var options, name, src, copy, copyIsArray, clone, target = arguments[0] || {}, i = 1, length = arguments.length, deep = false; // Handle a deep copy situation if ( typeof target === "boolean" ) { deep = target; target = arguments[1] || {}; // skip the boolean and the target i = 2; } // Handle case when target is a string or something (possible in deep copy) if ( typeof target !== "object" && !jQuery.isFunction(target) ) { target = {}; } // extend jQuery itself if only one argument is passed if ( length === i ) { target = this; --i; } for ( ; i < length; i++ ) { // Only deal with non-null/undefined values if ( (options = arguments[ i ]) != null ) { // Extend the base object for ( name in options ) { src = target[ name ]; copy = options[ name ]; // Prevent never-ending loop if ( target === copy ) { continue; } // Recurse if we're merging plain objects or arrays if ( deep && copy && ( jQuery.isPlainObject(copy) || (copyIsArray = jQuery.isArray(copy)) ) ) { if ( copyIsArray ) { copyIsArray = false; clone = src && jQuery.isArray(src) ? src : []; } else { clone = src && jQuery.isPlainObject(src) ? src : {}; } // Never move original objects, clone them target[ name ] = jQuery.extend( deep, clone, copy ); // Don't bring in undefined values } else if ( copy !== undefined ) { target[ name ] = copy; } } } } // Return the modified object return target; };