值传递和引用传递

1.值传递

    <script>
        var a = 1;
        var b = 2;
        function changeA(a,b){
            var tmp = a;
            a = b;
            b = tmp;
        }
        changeA(a,b);
        console.log(a,b);
    </script>

2.引用传递 function 和 Object

    <script>
        //Array 是Object
        var a = [1,2];
        function changeB(a){
            var tmp = a[0];
            a[0] = a[1];
            a[1] = tmp;
        }
        changeB(a);
        console.log(a);
    </script>