蛋疼....

[xss]

root@test:~# node test.js
100
300
true
100
true
100

root@test:~# cat test.js 
function Test(){
}
Test.prototype.v = 100;

var t = new Test();
console.log(t.v);
t.v = 300;

console.log(t.v);
console.log(delete t.v);
console.log(t.v);
console.log(delete t.v);
console.log(t.v);

delete operator

If a property with the same name exists on the object's prototype chain, then, after deletion, the object will use the property from the prototype chain (in other words, delete only has an effect on own properties).

[crazyxhz]

有啥问题？
delete：Return value
true for all cases except when the property is an own non-configurable property, in which case, false is returned in non-strict mode.

[gongbaodd]

没毛病，基于原型嘛

[xss]

@crazyxhz @gongbaodd 最后一次 delete 的时候理解上, 应该返回 false ?因为没有 use strict....

[crazyxhz]

@xss 非严格模式下，所有 delete 操作都范围 true，除非
使用 defineProperty 定义了一个 non-configurable 的属性，例如：
Object.defineProperty(obj, 'key', {
configurable: false
});
delete obj.key 在上面情况非严格模式下返回 false

在严格模式下，所有情况都返回 true，删除 non-configurable 的属性直接报错