一、typeof

console.log(typeof 1);               // number
console.log(typeof true);            // boolean
console.log(typeof 'mc');           // string
console.log(typeof function(){});    // function
console.log(typeof []);              // object 
console.log(typeof {});              // object
console.log(typeof
 
 null);            // object
console.log(typeof undefined);       // undefined

優點：能夠快速區分基本資料型別 缺點：不能將Object、Array和Null區分，都返回object

二、instanceof

console.log(1 instanceof Number);                    // false
console.log(true instanceof Boolean);                // false 
console.log('str' instanceof String);                //
 
 false  
console.log([] instanceof Array);                    // true
console.log(function(){} instanceof Function);       // true
console.log({} instanceof Object);                   // true

優點：能夠區分Array、Object和Function，適合用於判斷自定義的類例項物件 缺點：Number，Boolean，String基本資料型別不能判斷

三、Object.prototype.toString.call()

var toString = Object.prototype.toString;
 
console.log(toString.call(1));                      //[object Number]
console.log(toString.call(true));                   //[object Boolean]
console.log(toString.call('mc'));                  //[object String]
console.log(toString.call([]));                     //[object Array]
console.log(toString.call({}));                     //[object Object]
console.log(toString.call(function(){}));           //[object Function]
console.log(toString.call(undefined));              //[object Undefined]
console.log(toString.call(null));                   //[object Null]

優點：精準判斷資料型別 缺點：寫法繁瑣不容易記，推薦進行封裝後使用