变量数据类型

<script>
        var a = 888;
        console.log(typeof(a));//number
        var a = "888";
        console.log(typeof(a));//string
        var a = 2>1;
        //console.log(a);//true
        console.log(typeof(a));//boolean

        var obj = new Object();
        console.log(typeof(obj));//object
        var obj = new Array();
        console.log(typeof(obj));//object
        var obj = [];
        console.log(typeof(obj));//object

        var a = 123;
        a = null;//数值与数据类型统统为空，四大皆空
        console.log(null);

        console.log(typeof(b));//undefined

        function demo(){

        }
        console.log(typeof(demo));//function
    </script>