js对象标签

【proto】【class】【extensible】

proto就不多说了，每个对象都有一个proto默认指向Object.prototype

class标签：

var obj = {    x:1,    y:2};var tostr = Object.prototype.toString;console.log(tostr.call(null));//[object Null]console.log(tostr.call(obj));//[object Object]console.log(tostr.call(undefined));//[object Undefined]console.log(tostr.call(new Date()));//[object Date]