详解JavaScript中的4种类型识别方法

console.log(typeof "jerry");//"string"console.log(typeof 12);//"number"console.log(typeof true);//"boolean"console.log(typeof undefined);//"undefined"console.log(typeof null);//"object"console.log(typeof {name: "jerry"});//"object"console.log(typeof function(){});//"function"console.log(typeof []);//"object"console.log(typeof new Date);//"object"console.log(typeof //d/);//"object"function Person(){};console.log(typeof new Person);//"object"

function type(obj){　　return Object.prototype.toString.call(obj).slice(8,-1).toLowerCase();}  

console.log(Object.prototype.toString.call("jerry"));//[object String]console.log(Object.prototype.toString.call(12));//[object Number]console.log(Object.prototype.toString.call(true));//[object Boolean]console.log(Object.prototype.toString.call(undefined));//[object Undefined]console.log(Object.prototype.toString.call(null));//[object Null]console.log(Object.prototype.toString.call({name: "jerry"}));//[object Object]console.log(Object.prototype.toString.call(function(){}));//[object Function]console.log(Object.prototype.toString.call([]));//[object Array]console.log(Object.prototype.toString.call(new Date));//[object Date]console.log(Object.prototype.toString.call(//d/));//[object RegExp]function Person(){};console.log(Object.prototype.toString.call(new Person));//[object Object]

function type(obj){  return Object.prototype.toString.call(obj).slice(8,-1).toLowerCase();}console.log(type("jerry"));//"string"console.log(type(12));//"number"console.log(type(true));//"boolean"console.log(type(undefined));//"undefined"console.log(type(null));//"null"console.log(type({name: "jerry"}));//"object"console.log(type(function(){}));//"function"console.log(type([]));//"array"console.log(type(new Date));//"date"console.log(type(//d/));//"regexp"function Person(){};console.log(type(new Person));//"object"

function type(obj){  var temp = obj.constructor.toString();  return temp.replace(/^function (/w+)/(/).+$/,'$1');}

console.log(("jerry").constructor);//function String(){[native code]}console.log((12).constructor);//function Number(){[native code]}console.log((true).constructor);//function Boolean(){[native code]}//console.log((undefined).constructor);//报错//console.log((null).constructor);//报错console.log(({name: "jerry"}).constructor);//function Object(){[native code]}console.log((function(){}).constructor);//function Function(){[native code]}console.log(([]).constructor);//function Array(){[native code]}console.log((new Date).constructor);//function Date(){[native code]}console.log((//d/).constructor);//function RegExp(){[native code]}function Person(){};console.log((new Person).constructor);//function Person(){}

function type(obj){  var temp = obj.constructor.toString().toLowerCase();  return temp.replace(/^function (/w+)/(/).+$/,'$1');}console.log(type("jerry"));//"string"console.log(type(12));//"number"console.log(type(true));//"boolean"//console.log(type(undefined));//错误//console.log(type(null));//错误console.log(type({name: "jerry"}));//"object"console.log(type(function(){}));//"function"console.log(type([]));//"array"console.log(type(new Date));//"date"console.log(type(//d/));//"regexp"function Person(){};console.log(type(new Person));//"person"

console.log("jerry" instanceof String);//falseconsole.log(12 instanceof Number);//falseconsole.log(true instanceof Boolean);//false//console.log(undefined instanceof Undefined);//报错//console.log(null instanceof Null);//报错console.log({name: "jerry"} instanceof Object);//trueconsole.log(function(){} instanceof Function);//trueconsole.log([] instanceof Array);//trueconsole.log(new Date instanceof Date);//trueconsole.log(//d/ instanceof RegExp);//truefunction Person(){};console.log(new Person instanceof Person);//trueconsole.log(new Person instanceof Object);//true