instanceof 运算符用来检测 constructor.prototype 是否存在于参数 object 的原型链

instanceof

function Car(){}var car  = new Car()function Person(){}var person = new Person()console.log(car instanceof Car)     // trueconsole.log(car instanceof Object)  // trueconsole.log([] instanceof Array)    // trueconsole.log({} instanceof Object)   // true复制代码

• 封装typeOf 方法

  function myTypeOf(val) {	var toStr = Object.prototype.toString;	var type = typeof(val);	var res = {		'[object Array]': 'object array',		'[object Object]': 'object object',		'[object Number]': 'object number',		'[object String]': 'object string',		'[object Boolean]': 'object boolean'	}	if (type == null) {		return 'null';	} else if (type == 'object') {		var ret = toStr.call(val)		return res[ret];	} else {		return type;	}  }复制代码