js实现购物车数量的增加与减少，js实现购物车数量的自增与自减

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<title>js实现购物车数量的增加与减少，js实现购物车数量的自增与自减</title>

</head>

<body>

<center>

<table>

<tr>

<td>1</td>

<td><span onclick="changeNum(this,1)" style="cursor:pointer;">+</span><input type="text" value="" onblur="checknum(this)" /><span onclick="changeNum(this,-1)" style="cursor:pointer;">-</span></td>

</tr>

<tr>

<td>2</td>

<td><span onclick="changeNum(this,1)" style="cursor:pointer;">+</span><input type="text" value="" onblur="checknum(this)" /><span onclick="changeNum(this,-1)" style="cursor:pointer;">-</span></td>

</tr>

<tr>

<td>3</td>

<td><span onclick="changeNum(this,1)" style="cursor:pointer;">+</span><input type="text" value="" onblur="checknum(this)" /><span onclick="changeNum(this,-1)" style="cursor:pointer;">-</span></td>

</tr>

</table>

</center>

<script type="text/javascript">

function checknum(obj){

    if(obj.value >10){

        obj.value = 10;

        alert('Max 10!');

    }

}

function changeNum(obj,num)

{

    var input = getParent(obj).getElementsByTagName("input");

    for(var i=0;i<input.length;i++)

    {

        if(input[i].type=="text")

        {

            if(input[i].value == "")

                input[i].value = num;

            else

                input[i].value = input[i].value - 0 + num;

        }

        if(input[i].value == "-1")

                input[i].value = 0;

        if(input[i].value == "11")

                input[i].value = 10;

    }

}

//获取父级对像

function getParent(obj)

{

    if(typeof(obj) != "object"){obj = document.getElementById(obj);}

    if(obj)

        return obj.parentElement || obj.parentNode;

}

</script>

</body>

</html>