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Object.prototype.toString()能够很好的判断数据的类型及内置对象

• typeof xxx：能判断出number，string，undefined，boolean，object，function（null是object）
• Object.prototype.toString.call(xxx)：能判断出大部分类型
• Array.isArray(xxx)：判断是否为数组

var test= Object.prototype.toString;
console.log(test.call(1));//[object Number]
console.log(test.call("1"));//[object String]
console.log(test.call(false));//[object Boolean]
console.log(test.call({p:1}));//[object object]
console.log(test.call(undefined));//[object undefined]
console.log(test.call(null));//[object null]
console.log(test.call(function(){}));//[object Function]
console.log(test.call([1,2,3,4]));//[object Array]
console.log(test.call(new Date()));//[object Date]
console.log(test.call(new RegExp()));//[object RegExp]

 这里顺便提一下它的兄弟函数vaul