在JavaScript中也玩变量类型强行转换

<script language="javascript">    var str = '100';
    var num = Number(100);
    alert(typeof(num) + ': ' + num);
    var obj = Object(str);
    alert(typeof(obj) + ': ' + obj);
    var bool = Boolean(str);
    alert(typeof(bool) + ': ' + bool);
 
    var num = 100;
    var str = String(num);
    alert(typeof(str) + ': ' + str);
    var bool = Boolean(num);
    alert(typeof(bool) + ': ' + bool);
    var obj = Object(num);
    alert(typeof(obj) + ': ' + obj);
 
    var bool = true;
    var str = String(bool);
    alert(typeof(str) + ': ' + str);
    var num = Number(bool);
    alert(typeof(num) + ': ' + num);
    var obj = Object(bool);
    alert(typeof(obj) + ': ' + obj);
 
    var obj = {};
    var str = String(obj);
    alert(typeof(str) + ': ' + str);
    var num = Number(obj);
    alert(typeof(num) + ': ' + num);
    var bool = Boolean(obj);
    alert(typeof(bool) + ': ' + bool);
    </script>