js中一些特殊的运算符

var x = (1, 2, 3); alert(x);  //3 

var obj = {x: 1, y: 2}; obj.x;  //1 delete obj.x; obj.x;  //undefined 

注意：
1.delete不能删除configurable标签Ϊfalse的对象的属性:

var obj = {}; Object.defineProperty(obj, 'x', {     configurable: false,     value: 1 }); delete obj.x;  //false obj.x;  //1 

2.不能用于删除常量

var a = 1; delete a;  //false 

3.不能用于删除函数声明

function fun() {} delete fun;  //false 

var obj = {     name: 'person',     age: 20 }; 'name' in obj;  //true 

function Foo() {} Foo.prototype.x = 1; var obj = new Foo(); obj.x;  //1 obj.hasOwnProperty('x');  //false obj.__proto__.hasOwnProperty('x');  //true 

构造对象？？？所以，没对象，new一个？哈哈，不要太方便！

END!

文章来源: js中一些特殊的运算符