js中的delete

先来抛一个例子

var a = 1;
b = 2;
function fn(){
    c = 3;
}
fn()
console.log(a) //1
console.log(b) //2
console.log(c) //3
delete a;
delete b;
delete c;
console.log(typeof a) //number
console.log(typeof b) //undefined
console.log(typeof c) //undefined

说明：在全局作用域中使用var创建的全局变量是不能被delete删除的

可以删除对象的某个属性:

var o = { x: 1 };  
delete o.x; // true  
o.x; // undefined  

但不能删除变量,比如以下面这种方式声明的:

var x = 1;  
delete x; // false  
x; // 1  

也不能删除函数,比如下面所定义的:

function x(){}  
delete x; // false  
typeof x; // "function"  

删除不了原型链中的变量

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