js 变量的定义及其有效范畴 _JavaScript

js 变量的定义及其有效范围
<html>
<head>
<script type="text/javascript">
function myfunction()
{
    obj = 0;
    var obj1 = 0;
    obj2 = 0;
    document.write("before invoking<br>");
    document.write("obj = "+obj+"<br>") // 0
    document.write("obj1 = "+obj1+"<br>") // 0
    document.write("obj2 = "+obj2+"<br>") // 0
    func1();
    document.write("after invoking<br>");
    document.write("obj = "+obj+"<br>") // 1
    document.write("obj1 = "+obj1+"<br>") // 0
    document.write("obj2 = "+obj2+"<br>") // 0
}
function func1(){
     obj = 1;
     obj1 = 1;
     var obj2 = 1;
}
</script>
</head>
<body onload="myfunction()">
</body>
</html>