JavaScript 判斷對象類型的方法

typeof(最基本的)

typeof 只能檢查出來以下7幾種類型：

• Undefined ————“undefined”
• Null ————“object” (見下方)
• 布爾值 ————“boolean”
• 數值 ————“number”
• 字符串 ————“string”
• 函數對象 (implements [[Call]] in ECMA-262 terms) ————“function”
• 任何其他對象 ————“object”

	console.log(typeof a);    //'undefined'

    console.log(typeof(true));  //'boolean'

    console.log(typeof '123');  //'string'

    console.log(typeof 123);   //'number'

    console.log(typeof NaN);   //'number'

    console.log(typeof null);  //'object'    

    var obj = new String();

    console.log(typeof(obj));    //'object'

    var  fn = function(){};

    console.log(typeof(fn));  //'function'

    console.log(typeof(class c{}));  //'function'

	console.log(typeof(new Boolean(0)));//object

Object.prototype.toString.call()

call/bind/apply的用法

var a = "hello world";
var b = [];
var c = function(){};

console.log( Object.prototype.toString.call( a ) );
console.log( Object.prototype.toString.call( b ) );
console.log( Object.prototype.toString.call( c ) );

//結果
[object String];
[object Array];
[object Function];

instanceof

functionPerson(){};
functionStudent(){};
var p =new Person();
Student.prototype=p;//繼承原型
var s=new Student();
console.log(s instanceof Student);//trueconsole.log(s instanceof Person);//true