Two examples using for...in loop

<script type="text/javascript">

    var a = [1, 3, 5, 6, 33];

    for(ele in a) {

       document.write(ele + ": " + a[ele]);

       document.write("<br/>");

    }

    for(i=0; i< a.length; i++) {

        document.write(i + ": " + a[i]);

        document.write("<br/>");

    }

</script>

    <script type="text/javascript">

        var json = {

            "name" : "中国移动",

            "sex" : "阴阳",

            "口碑" : "负数"

        };

        for ( var p in json) {

            document.writeln("prop：" + p + ", value：" + json[p] + "<br/>\n");

        }

    </script>

    <script type="text/javascript">

        var json = {

            name : "中国移动",

            sex : "阴阳",

            口碑 : "负数",

 sayHi: function(a) {

     alert(a);

 }

        };

        for ( var p in json) {

            document.writeln("prop：" + p + ", value：" + json[p] + "<br/>\n");

        }

    </script>

prop：name, value：中国移动

prop：sex, value：阴阳

prop：口碑, value：负数

prop：sayHi, value：function(a) { alert(a); }