js数据类型判断

js数据类型判断

 

Object.prototype.toString.call(data)

var bool = true
var num = 1
var str = 'abc'
var und = undefined
var nul = null
var arr = [1,2,3]
var obj = {name:'haoxl',age:18}
var fun = function(){console.log('I am a function')}

console.log(Object.prototype.toString.call(bool));//[object Boolean]
console.log(Object.prototype.toString.call(num));//[object Number]
console.log(Object.prototype.toString.call(str));//[object String]
console.log(Object.prototype.toString.call(und));//[object Undefined]
console.log(Object.prototype.toString.call(nul));//[object Null]
console.log(Object.prototype.toString.call(arr));//[object Array]
console.log(Object.prototype.toString.call(obj));//[object Object]
console.log(Object.prototype.toString.call(fun));//[object Function]

function Person(){}
function Student(){}
Student.prototype = new Person()
var haoxl = new Student()
console.log(Object.prototype.toString.call(haoxl));//[object Object]

//原理(摘自高级程序设计3)：在任何值上调用 Object 原生的 toString() 方法，都会返回一个 [object NativeConstructorName] 格式的字符串。每个类在内部都有一个 [[Class]] 属性，这个属性中就指定了上述字符串中的构造函数名。
//但是它不能检测非原生构造函数的构造函数名。

 

使用jquery中的$.type

console.log($.type(bool));//boolean
console.log($.type(num));//number
console.log($.type(str));//string
console.log($.type(und));//undefined
console.log($.type(nul));//null
console.log($.type(arr));//array
console.log($.type(obj));//object
console.log($.type(fun));//function

function Person(){}
function Student(){}
Student.prototype = new Person()
var haoxl = new Student()
console.log($.type(haoxl));//object

// $.type()内部原理就是用的Object.prototype.toString.call()