JaveScript基础之变量和变量类型

变量使用

<script type="text/javascript">
    // 定义一个数字变量
    var x;
    x = 50;
    //还可以这样
    var x = 50;
    //定义一个字符串变量
    var name = '我是谁';
</script>

<script type="text/javascript">
    var a = 50;
    var b = 1.3;
    var c = -1;
    alert(a);
    alert(typeof a);
    alert(b);
    alert(typeof b);
    alert(c);
    alert(typeof c);
</script>

常用变量类型

1. number 类型

<script type="text/javascript">
    var a = 50;
    var b = 1.3;
    var c = -1;
    alert(a);
    alert(typeof a);
    alert(b);
    alert(typeof b);
    alert(c);
    alert(typeof c);
</script>

2. string 类型

<script type="text/javascript">
    var name="Hunter9000";
    alert(name);
    alert(typeof name);
</script>

3. undefined 类型

<script type="text/javascript">
    var y;
    alert(y);
    alert(typeof y);
</script>

4. null 类型

<script type="text/javascript">
    var x = null;
    alert(x);
    alert(typeof x);
</script>

5. boolean 类型

<script type="text/javascript">
    x = 3 > 4;
    alert(x);
    alert(typeof x);
</script>