首页 > 代码库 > JS判断对象类型
JS判断对象类型
对于确定JS内置对象类型，JS提供了typeof运算符，该运算符得到的结果为以下6种:number,boolean,string,function,object,undefined.不过对绝大多数对象而言，typeof都返回"object",无法确定具体的类型。我们使用一种函数Object.prototype.toString.call来判断
<script> var a = 1; console.log("a:"+typeof a); //number console.log("a:"+Object.prototype.toString.call(a)); //[object Number] var b = NaN; console.log("b:"+typeof b); //number console.log("b:"+Object.prototype.toString.call(b)); //[object Number] var c= Number.MIN_VALUE; console.log("c:"+typeof c); //number console.log("c:"+Object.prototype.toString.call(c)); //[object Number] var d= Infinity; console.log("d:"+typeof d); //number console.log("d:"+Object.prototype.toString.call(d)); //[object Number] var e= "pmx"; console.log("e:"+typeof e); //string console.log("e:"+Object.prototype.toString.call(e)); //[object String] var f= true; console.log("f:"+typeof f); //boolean console.log("f:"+Object.prototype.toString.call(f)); //[object Boolean] var g= window; console.log("g:"+typeof g); //object console.log("g:"+Object.prototype.toString.call(g)); //[object Window] var h = [1]; console.log("h:"+typeof h); //object console.log("h:"+Object.prototype.toString.call(h)); //[object Array] var i = function(){}; console.log("i:" + typeof i); //function console.log("i:"+Object.prototype.toString.call(i)); //[object Function] var j = document; console.log("j:" + typeof j); //object console.log("j:"+Object.prototype.toString.call(j)); //[object HTMLDocument] var k = null; console.log("k:" + typeof k); //object console.log("k:"+Object.prototype.toString.call(k)); //[object Null] var l = undefined; console.log("l:" + typeof l); //undefined console.log("l:"+Object.prototype.toString.call(l)); //[object Undefined] var m = eval; console.log("m:" + typeof m); //function console.log("m:"+Object.prototype.toString.call(m)); //[object Function] var n = new Date(); console.log("n:" + typeof n); //object console.log("n:"+Object.prototype.toString.call(n)); //[object Date] </script>
将Object.prototype.toString.call的返回值处理下，使得更直观
<script>var class2type = {}; var types = "Boolean Number String Function Array Date RegExp Object Error".split(" "); for(var i=0; i<types.length; i++){ class2type["[object "+types[i]+"]"] = types[i].toLowerCase(); } function type(obj){ var type = Object.prototype.toString.call(obj); return class2type[type]; }console.log(type([1]));//array</script>
JS中还有个类似的运算符instanceof,它是用来判断某个对象是否是某类型的实例
<script> var a = function(){} console.log(a instanceof Object);//true var b = 1; console.log(b instanceof Object);//false var c = "1"; console.log(c instanceof Object);//false var d = true; console.log(d instanceof Object);//false var e = undefined; console.log(e instanceof Object);//false var f = null; console.log(f instanceof Object);//false var g = [1]; console.log(g instanceof Object);//true var h = window; console.log(h instanceof Object);//gte IE 9:true，lt IE 9:false </script>
可以看到，JS中的5中基本类型number,string,boolean,undefined,null并不是Object的实例。
对于低版本的浏览器认为window对象是dom里面的属性，和JS对象是两码事
JS判断对象类型
声明：以上内容来自用户投稿及互联网公开渠道收集整理发布，本网站不拥有所有权，未作人工编辑处理，也不承担相关法律责任，若内容有误或涉及侵权可进行投诉： 投诉/举报 工作人员会在5个工作日内联系你，一经查实，本站将立刻删除涉嫌侵权内容。