<script>
    var arr1 = ['aaa','bbbb','//www.49028c.com'];
    alert(arr1);
    arr1.length = 0;
    alert(arr1); //數組為空
</script>

<script>
    var arr1 = ['aaa','bbbb','c','d','e'];
    arr1.length = 3;
    alert(arr1); //截斷數組aaa,bbbb,c
</script>