JAVASCRIPT中经典面试题

//1、try catch finally中的return
var n=1;
function fun(){
try{
n++;
m++;//报错
return n;
}catch(err){
n++;
return n;
}finally{
n++;
//return n;
}
}
console.log(fun());//3
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

/*new Function*/
var i=5;
function fun(){
var i=4;
//var f1=new Function("console.log(i)");
var f1=function(){console.log(i);};
console.log(f1);
f1();
}
fun();//4

/*callback 与 this*/
var o={
n:1,
fun:function(){
var self=this;//留住this
console.log(self.n++);
setTimeout(function(){
self.fun();
},1000);
}
}
o.fun();//this-->o

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

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

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

/*私有属性，公有属性*/
function Student(){
var prop="私有属性";//私有属性
this.prop="公有属性"; //公有属性
var fun=function(){//私有方法
console.log("调用私有方法");
console.log(prop);
}
this.fun=function(){//公有方法
console.log("调用公有方法");
fun();//this-->window
console.log(prop);
console.log(this.prop);
}
}
var lilei=new Student();
lilei.fun();//公有

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

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

/**/
function fun(n,o){
console.log(o);
return {fun:function(m){
return fun(m,n);
}
}
}
var a=fun(0);//undefined
//a-->{fun:function(m){return fun(m,n)}}
a.fun(1); a.fun(2); a.fun(3); //0 0 0
var b=fun(0).fun(1).fun(2).fun(3); //0 1 2
var c=fun(0).fun(1); c.fun(2);c.fun(3); //0 1 1