$.extend.apply( null, [ true, { "a" : 1, "b" : 2 } ] );
//console.log(window.a);
//window.location.reload(); $.extend.apply( null, [ true, { "a" : 1, "b" : 2 } ].concat( { "c" : 3, "d" : 4 } ) ); //console.log(window.a)
一、问题：
1. null在这里是干啥？
2. window.a分别是什么？
二、我们先一起来了解下jQuery中的extend函数
在jQuery-V1.2.6中：
jQuery.extend = jQuery.fn.extend = function() { // copy reference to target object var target = arguments[0] || {}, i = 1, length = arguments.length, deep = false, options; // Handle a deep copy situation if ( target.constructor == 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" && typeof target != "function" ) 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 ( var name in options ) { var src = target[ name ], copy = options[ name ]; // Prevent never-ending loop if ( target === copy ) continue; // Recurse if we're merging object values if ( deep && copy && typeof copy == "object" && !copy.nodeType ) target[ name ] = jQuery.extend( deep, // Never move original objects, clone them src || ( copy.length != null ? [ ] : { } ) , copy ); // Don't bring in undefined values else if ( copy !== undefined ) target[ name ] = copy; } // Return the modified object return target; };