数值交换

 <script>
        //第一种方法
        var a = 2;
        var b = 3;
        var c = a;
        a = b;
        b = c;
        console.log(a);
        console.log(b);

        //第二种方法
        var a = 2;
        var b = 3;
        a = a + b; //5
        b = a - b; //5-3
        a = a - b; //5-2
        console.log(a);
        console.log(b);
    </script>