//&&得到的结果不是布尔类型，如果前面都是 true就执行最后一个，并返回最后一个表达式的值，前面有一个为false,后面不执行，返回前面表达式的值var a = 3;var b = a && (a = 4);console.log(b);//4var b = a && (a ++);console.log(a);//5console.log(b);//4a && (a ++);console.log(a);//6var c = 0;var d = c && a++;console.log(a);//6console.log(d);//0var c = 0;var d = b && c && a++;console.log(a);//6console.log(d);//0var c = false;var d = b && c && a++;console.log(a);//6console.log(d);//false// || 前面是true，后面不执行，返回前面表达式值。前面是false,返回后面表达式的值var a1 = 3;var b1 = a1 || a1++;console.log(a1);//3console.log(b1);//3var a1 = 0;var b1 = a1 || a1++;console.log(a1);//1console.log(b1);//0====================================================================//浅拷贝，指向同一个内存区域var person ={     name:"cj",     age:22,     address:{         home:"home address",         office:"office address"     },     schools:["xiaoxue","daxue"] };var programer = {     language:"javascript" };//全部复制function  extend (p,c) {     var c = c ||{}; //如果c是undefined或者null,就是{}     for(var prop in p){         c[prop] = p[prop];//如果有属性值是对象，则是把地址复制过去了，     }}extend(person,programer);console.log(programer.address);//{home: "home address", office: "office address"}console.log(programer.address.home);//home addressconsole.log(programer.schools);//["xiaoxue", "daxue"]programer.name = "sss";console.log(person.name);//cjprogramer.address.name = "xxx";console.log(person.address.name);//xxxprogramer.schools[0] = "iii";console.log(person.schools[0]);//iiiconsole.log(person.schools[0]);//iii=====================================================//深拷贝，跟父类没关系了function extendDeeply(p,c){
   //from --> to      var c = c|| {};     for(var prop in p){
   //{}形式的对象可以用for in循环，prop是key，p[prop]是每一个value。json和数组都可以用for in循环，数组时候prop是0,，1，2,3，json时候prop是key         if(typeof p[prop] === "object"){             c[prop] = (p[prop].constructor ===Array)?[]:{};//c[address]={}             extendDeeply(p[prop],c[prop]);//p[address],c[address]                     }else{             c[prop] = p[prop];//给c新增一个key和value,c[address][home]=p[address][home]         }    }}================================================================function Parent(){      this.name = "abc";      this.address = {home:"home"};}function Child(){
   //可以看成类，对象，构造函数，函数执行是相当于构造函数执行但是要return function才产生对象。     Parent.call(this);//this就有了Parent的属性了，深拷贝      this.language = "java";}var c = new Child();c.address.home = "ssss"var p = new Parent();console.log(p.address.home);//home=================================================================    //原型链;java里面的继承关系，一直找到Object类去    var p ={name:"cj"};    function myCreate(p){        var ins ;        function F(){};        F.prototype = p;//函数的原型指向p对象，函数公有区域指向p对象，所以ins.__proto__指向p对象，就实现了继承。        ins =  new F();        return ins ;    }//对象的__proto__ 指向的是//对象的构造器constructor//的原型对象（prototype）//但原型对象并不是能用上面的话来说明//原型对象的__proto__指向的是Object得prototype//而不是指向//其(Object.prototype)构造器constructor ==某个函数//的原型对象

function FF(){};   var ff = new FF(){};   ff.__proto__ === FF.prototype;//true    ff.__proto__  === ff.constructor.prototype;  //true    FF.prototype.__proto__ ===FF.prototype.constructor.prototype; //false