未捕获的TypeError：undefined不是函数调用JavaScript函数

Question

I am get the error: Uncaught TypeError: undefined is not a function when I am trying to call my Javacsript function displayValue() .

Here is my Javascript code:

    var HoC = 0;
    var Rate = 0;

    function getHoursOrCubes(input, control)
    {
        HoC = input;
        var answer = HoC * Rate;
        displayValue(answer);
    }

    function getRate(input, control)
    {
        Rate = input;
        var answer = HoC * Rate;
        displayValue(answer);
    }

    function displayValue(finalValue) {
        var listViewRef = document.getElementById('LV_Tickets');
        var elementArray = listViewRef.getElementsByTagName('Label');
        alert('this worked.');

        for (var i = 0; i < elementArray.length; i++) {
            var elementRef = elementArray[i];

            elementRef.value = finalValue;
            alert(elementRef.value);
        }
    }

I believe the line that is throwing the error is var elementArray = listViewRef.getElementsByTagName('Label'); .

I have a listview inside a listview and I want to set the value of a label in the nested listview. So that is what I am trying to do here.

Here is my asp code for the ListView I am trying to access:

<asp:ListView ID="LV_Tickets" runat="server" DataSourceID="SQL_Tickets"  InsertItemPosition="FirstItem" OnPreRender="LV_Tickets_PreRender" DataKeyNames="TicketNum">

The getHoursOrCubes() function is called in a nested ListView's insertingitem template:

<asp:TextBox ID="HoursOrCubesTextBox" runat="server" style="height: 20px; width: 165px;" Text='<%# Bind("HoursOrCubes") %>' onchange="getHoursOrCubes(this.value)" />

Answer 1

    var listViewRef = document.getElementById(<%= LV_Tickets.ClientID %>);
    var elementArray = listViewRef.getElementsByTagName('Label');

listViewRef is a nodeList that means it's a collection of nodes. To call the function getElementsByTagName you need a node. I selected the first node in the list by [0] . This should return a node on which getElementsByTagName can be called.

Answer 2

You're trying to call a function that doesn't exist.

The function getElementsByName returns an IHTMLElementCollection . Use the tags method of that object to get what you want. There is no method for getElementsByTagName that operates on the IHTMLElementCollection .

Instead of

var elementArray = listViewRef.getElementsByTagName('Label');

try

var elementArray = listViewRef.tags('Label');

That should work for you.