JAVASCRIPT中经典面试题

 1 //1、try catch finally中的return
 2     var n=1;
 3     function fun(){
 4         try{
 5             n++;
 6             m++;//报错
 7             return n;
 8         }catch(err){
 9             n++;
10             return n;
11         }finally{
12             n++;
13             //return n;
14         }
15     }
16     console.log(fun());//3
17     console.log(n);//4

/*作用域和作用域链*/
	var n=10;
	function fun(n){
		n--;
		console.log(n);
	}
	console.log(fun(n)); //9
	console.log(n); //10

 1 /*new Function*/
 2     var i=5;
 3     function fun(){
 4         var i=4;
 5         //var f1=new Function("console.log(i)");
 6         var f1=function(){console.log(i);};
 7         console.log(f1);
 8         f1();
 9     }
10     fun();//4

 1 /*callback 与 this*/
 2     var o={
 3         n:1,
 4         fun:function(){
 5             var self=this;//留住this
 6             console.log(self.n++);
 7             setTimeout(function(){
 8                 self.fun();
 9             },1000);
10         }
11     }
12     o.fun();//this-->o

1 /*DOM中的闭包问题*/
2     function fun(){
3         var li=document.getXX...;
4         btn.onclick=function(){
5             li.xx=xx;
6         }//li将永远无法释放，即使刷新页面也不行
7     }

1 /*引用类型的共有属性*/
2     function Student(){}
3     Student.prototype.arr=[];
4     var lilei=new Student();
5     var hmm=new Student();
6     lilei.arr.push(1);//this[this.length]=1
7     hmm.arr[1]=2;
8     console.log(lilei.arr);//[1,2]
9     console.log(hmm.arr);//[1,2]

1 /*继承父类型共有方法*/
2     function Student(){}
3     Student.prototype=[];
4     var lilei=new Student();
5     lilei.push(1);//this[this.length]=value;
6     var hmm=new Student();
7     hmm.push(2);
8     console.log(lilei);
9     console.log(hmm);

 1 /*私有属性，公有属性*/
 2     function Student(){
 3         var prop="私有属性";//私有属性
 4         this.prop="公有属性"; //公有属性
 5         var fun=function(){//私有方法
 6             console.log("调用私有方法");
 7             console.log(prop);
 8         }
 9         this.fun=function(){//公有方法
10             console.log("调用公有方法");
11             fun();//this-->window
12             console.log(prop);
13             console.log(this.prop);
14         }
15     }
16     var lilei=new Student();
17     lilei.fun();//公有

1 //阻碍事件
2 for(var i=0;i<3;i++){
3         setTimeout(function(){
4             console.log(i);
5         },10)
6     }
7     alert("hello");

 1 function MyObj(){
 2         this.p.pid++;
 3     }
 4     MyObj.prototype.p={"pid":0};
 5     MyObj.prototype.getNum=function(num){
 6         return this.p.pid+num;
 7     }
 8     var obj1=new MyObj(); 
 9     var obj2=new MyObj(); //p.pid=2
10     console.log(obj1.getNum(1)+obj2.getNum(2));//7

 1 /**/
 2     function fun(n,o){
 3         console.log(o);
 4         return {fun:function(m){
 5                 return fun(m,n);
 6             }
 7         }
 8     }
 9     var a=fun(0);//undefined
10     //a-->{fun:function(m){return fun(m,n)}}
11     a.fun(1); a.fun(2); a.fun(3); //0 0 0
12     var b=fun(0).fun(1).fun(2).fun(3); //0 1 2
13     var c=fun(0).fun(1); c.fun(2);c.fun(3); //0 1 1