1.对象属性删除

function fun(){

this.name = 'mm';

}

var obj = new fun();

console.log(obj.name);//mm

delete obj.name;

console.log(obj.name); //undefined

　　2.变量删除

var name = 'lily';
delete name;
console.log(name); //lily

　　直接用delelte删除不了变量

　　3.删除不了原型链中的变量

fun.prototype.age = 18;
delete obj.age;
console.log(obj.age) //18