JavaScript 数据类型梳理

编辑时间：2019-02

JavaScript 的数据类型有 7 种

  1 Undefined
  2 Null
  3 Boolean
  4 String
  5 Number
  6 Symbol ( ES6 新增 )
  7 Object

typeof 的返回值有 7 种

  1 "undefined"
  2 "boolean"
  3 "string"
  4 "number"
  5 "symbol" ( ES6 新增 )
  6 "object"
  7 "function"

常见数据的类型对照表

value	typeof 结果	对应类型
var a; window.undefined;	typeof a == “undefined”; typeof window.undefined == “undefined”; typeof x == “undefined”;	Undefined
var b = false;	typeof b == “boolean”;	Boolean
var s = “”;	typeof s == “string”;	String
var n = 1;	typeof n == “number”;	Number
var s = Symbol(“s”);	typeof s == “symbol”;	Symbol
var o = {}; var nu = null;	typeof o == “object”; typeof nu == “object”;	Object Null
var f = function(){};	typeof f == “function”	--

具体类型判断

  1 Object.prototype.toString.call(2) // "[object Number]"
  2 Object.prototype.toString.call('') // "[object String]"
  3 Object.prototype.toString.call(true) // "[object Boolean]"
  4 Object.prototype.toString.call(undefined) // "[object Undefined]"
  5 Object.prototype.toString.call(null) // "[object Null]"
  6 Object.prototype.toString.call(Math) // "[object Math]"
  7 Object.prototype.toString.call({}) // "[object Object]"
  8 Object.prototype.toString.call([]) // "[object Array]"
  9 Object.prototype.toString.call(function(){}) // "[object Function]"
 10 // 参考：http://javascript.ruanyifeng.com/stdlib/object.html#toc8