jquery源码阅读之jquery.extend

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jquery.extend 在众多插件中都有应用，最常见的应用是把插件默认的参数和用户输入的参数进行合并，用户没有输入的参数则用插件默认的参数，设置了，则采用用户设置的参数;

首先我们看看jquery.extend API的解释：这里

测试代码：

<!doctype html><html lang="en"><head>  <meta charset="utf-8">  <title>jQuery.extend demo</title><script src="../jquery-1.7.1.js"></script>   <script src="../bobojq.js"></script></head><body> <div id="log"></div> <script>var object1 = {  apple: 0,  banana: { weight: 52, price: 100 },  cherry: 97};var object2 = {  banana: { price: 200 },  durian: 100};var o = {};o.n1 = o;$.extend(true,o,{n2:o}); //测试无线循环//$.extend( object1, object2 );//非深度$.extend( true, object1, object2 );//深度 // Assuming JSON.stringify - not available in IE<8$( "#log" ).append( JSON.stringify( object1 ) );</script> </body></html>

jquery.extend 源码阅读：

jQuery.extend = jQuery.fn.extend = function() {var src, copyIsArray, copy, name, options, clone,target = arguments[0] || {},i = 1,length = arguments.length,deep = false;// Handle a deep copy situation 如过第一个参数是布尔值则调整修正参数顺序 例如$.extend( true, object1, object2 ); if ( typeof target === "boolean" ) {deep = target;target = arguments[1] || {};// skip the boolean and the targeti = 2;}// Handle case when target is a string or something (possible in deep copy) //对于目标对象非对象和函数的，例如字符串修成为对象if ( typeof target !== "object" && !jQuery.isFunction(target) ) {target = {};}// extend jQuery itself if only one argument is passed //如果只有一个对象参数则认和jquery合并if ( length === i ) {target = this;--i;}for ( ; i < length; i++ ) {// Only deal with non-null/undefined valuesif ( (options = arguments[ i ]) != null ) {// Extend the base objectfor ( name in options ) {src = target[ name ];copy = options[ name ];// Prevent never-ending loop 防止进入无线循环if ( target === copy ) {continue;}// Recurse if we're merging plain objects or arrays 深度和非深度的区别/*var object1 = {apple: 0,banana: { weight: 52, price: 100 },cherry: 97};var object2 = {banana: { price: 200 },durian: 100};$.extend(object1,object2) {"apple":0,"banana":{"price":200},"cherry":97,"durian":100}$.extend(true,object1,object2) {"apple":0,"banana":{"weight":52,"price":200},"cherry":97,"durian":100}*/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 themtarget[ name ] = jQuery.extend( deep, clone, copy );// Don't bring in undefined values} else if ( copy !== undefined ) { // 一般常用的是这个target[ name ] = copy;}}}}// Return the modified objectreturn target;};

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