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我的页面上有两个列表框，我需要在 javascript 的帮助下在它们之间移动项目。这是我的标记：

<asp:ListBox ID="ListBox1" Height="300px" runat="server" AppendDataBoundItems="true" 
        SelectionMode="Multiple"></asp:ListBox>

<div>

<asp:ImageButton ID="ButtonRight" runat="server" ImageUrl="~/Images/right.gif" OnClientClick="return     
      LeftToRightMoveItems('AddSetup');" /><br />
<br />
<asp:ImageButton ID="ButtonLeft" runat="server" ImageUrl="~/Images/left.gif" OnClientClick="return 
       RightToLeftMoveItems('AddSetup');" />
</div>

<asp:ListBox ID="ListBox2" Height="300px" runat="server" AppendDataBoundItems="true"  
      SelectionMode="Multiple"></asp:ListBox>

这是我的 JavaScript 代码：

Javascript：

 function LeftToRightMoveItems() {
        try {
            if (status == "AddSetup") {
                var varFromBox = document.getElementById("<%=ListBox1.ClientID%>").options;
                var varToBox = document.getElementById("<%=ListBox2.ClientID%>").options;
            }

            alert(varFromBox.length);
            alert(varToBox.length);

            if ((varFromBox != null)) {
                if (varFromBox.length < 1) {
                    alert('There are no items to move!');
                    return false;
                }
                if (varFromBox.options.selectedIndex == -1) // when no Item is selected the index will be -1
                {
                    alert('Please select an item to move!');
                    return false;
                }
                while (varFromBox.options.selectedIndex >= 0) {
                    var newOption = new Option(); // Create a new instance of ListItem 
                    newOption.text = varFromBox.options[varFromBox.options.selectedIndex].text;
                    newOption.value = varFromBox.options[varFromBox.options.selectedIndex].value;
                    varToBox.options[varToBox.length] = newOption; //Append the item in Target Listbox
                    varFromBox.remove(varFromBox.options.selectedIndex); //Remove the item from Source Listbox
                }
            }
        }
        catch (e) {
            alert("Following error occured : \n" + e.description);
        }
        return false;
    }

在页面加载时，我正在填写ListBox1. 但是在alert()我得到0个项目。

HTML 看起来像：

<SELECT style="HEIGHT: 300px" id=ListBox1 multiple size=4 name=ctl00$ContentPlaceHolderNewSys$TabContainerMain$tabPanelAdd$tabContainerInnerAdd$tabPanelAdd_1$ListBoxAll1> <OPTION value=1>param1</OPTION> <OPTION value=2>param2</OPTION> <OPTION value=3>param3</OPTION></SELECT>
4

1 回答 1

1

该函数不接受状态参数。修改函数的签名以接受status作为参数。

function LeftToRightMoveItems(status) {
...
}

提供状态后，代码也存在一些问题。主要是varFromBox当它实际表示一组选项时，它被用作选择。

例如，varFromBox最初声明为对象数组：

var varFromBox = document.getElementById("<%=ListBox1.ClientID%>").options;

然后在不同的地方，代码尝试访问 options 属性，就好像varFromBox是一个 select 元素。实际上它实际上是在寻找options.options

 while (varFromBox.options.selectedIndex >= 0) {..}

这是我想出的否定这些问题的方法。我删除了 try/catch，因此任何错误都更加明显。还要检查这个例子：http: //jsfiddle.net/7dVyq/

function LeftToRightMoveItems(status){

                if (status == "AddSetup") {
                    var varFromBox = document.getElementById("ListBox1").options;
                    var varToBox = document.getElementById("ListBox2");
                }

                alert(varFromBox.length);
                alert(varToBox.length);

                if ((varFromBox != null)) {
                    if (varFromBox.length < 1) {
                        alert('There are no items to move!');
                        return false;
                    }
                    console.log(varFromBox.selectedIndex);
                    if (varFromBox.selectedIndex == -1) // when no Item is selected the index will be -1
                    {
                        alert('Please select an item to move!');
                        return false;
                    }
                    for (var i = 0; i < varFromBox.length; i++) {
                        if (varFromBox[i].selectedIndex != -1) {
                            var newOption = new Option(); // Create a new instance of ListItem
                            newOption.text = varFromBox[i].text;
                            newOption.value = varFromBox[i].value;
                            varToBox.options[varToBox.length] = newOption; //Append the item in Target Listbox
                            document.getElementById("ListBox1").remove(varFromBox[i]); //Remove the item from Source Listbox
                        }
                    }
                    return false;
                }
            }
于 2012-12-05T08:09:22.590 回答