When accessing `document.getElementById()` from an external JavaScript file, it may sometimes return a value

On my aspx page, I am calling the 123.js file from within the solution. Here is how it looks:

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="1.aspx.cs" Inherits="1"  ValidateRequest="false"%>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <script src="Scripts/123.js" type="text/javascript"></script>
    .
    .
    .
    .
    <tr>
     <td>Start DateTime</td>
     <td>
      <asp:TextBox ID="txtStartDateTime" runat="server"></asp:TextBox>                                
     </td>
     <td>                                    
       <a href="javascript:_fnSet('this', 'txtStartDateTime', 'close=true,instance=single')">                                         
       <img src="Styles/imagesCA3B3R54.jpg" alt="IMG" style="border-style: none" />                                         
       </a>
      </td>
    </tr>
</asp:Content>

The function fnSet() can be found in 123.js and it starts with:

function _fnSet(e, sInputID, sCustom) {
    var oInput = document.getElementById(sInputID);
}

Even though sInputID contains the value 'txtStartDateTime' as a string, the oInput variable returns null.

Why is this happening..???

Answer №1

When working with ContentPlaceHolders in ASP.NET, it's important to keep in mind the way that ClientID is generated for controls on the client side. The default behavior of ASP.NET is to append an extra identifier to the Control's ID, known as the ClientID. You have the ability to modify how the ClientID is generated by adjusting the ClientIDMode property. Experiment with changing the ClientIDMode to Static.

<asp:TextBox ID="txtStartDateTime" ClientIDMode="Static" runat="server" />

If you ever find yourself unsure about the exact ID being used on the client side, simply view the page in your browser and inspect the HTML code that has been generated.

To ensure consistency, consider setting the ClientIdMode to static as the default option in your web.config file.

<pages clientIDMode="static" />

Answer №2

The ID of txtStartDateTime has been altered. Please refer to the source code.

If you wish to retrieve the ClientID, you can use the following method:

document.getElementByID('<%# txtStartDateTime.ClientID %>')

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

What is the best way to divide an array into separate columns in JavaScript?

Hey there fellow JavaScript enthusiasts! I am working with an array that I created from data extracted from a csv file. Here's a snippet of how it looks: https://i.sstatic.net/tczVz.png Each index in the array, for example array[0], represents the ...

The functionality of HTML5 Camera is experiencing issues while being used with Tomcat7

My Angular2 project includes HTML5 camera access functionality. I launch the project using Angular CLI (ng serve), which starts the web container for testing purposes. When trying to access the camera, the browser prompts me for permission. Once granted, e ...

Mongoose Troubles in NodeJS

I am reaching out to seek assistance with a problem I am facing that I have been unable to resolve on my own. My tech stack includes nodejs, express, and mongodb (particularly using mongoose). Although my express server is running smoothly, I am encounter ...

Is it possible for me to derive a generic class from a generic type T? For example, MyClass<T>: T

I am aiming to accomplish something similar to the code snippet below. However, Visual Studio is flagging an error and I am uncertain how to resolve it: public abstract class My_BaseControl<T> : T, IRightBasedUsability where T : System.Web ...

Implementing server-side pagination with Ngrx and using router parameters to navigate pages

In my store, I have a simplified state tree structure: { routerReducer: { state: { url: '/blog' }, queryParams: { category: 'home' } params: { } }, blog: { ...

Switch the checkbox to a selection option

Is there a way to switch the selection method from checkboxes to a dropdown menu? $("input[name=koleso]:first").prop("checked", true); $('body').on('click', '.koleso label', function (e) { koles ...

Angular Checkbox Single Select

I have a piece of HTML code with ng-repeat that includes checkboxes. <table> <tr ng-repeat="address in contactInfo.Addresses"> <td>{{address.DisplayType}}</td> <td>{{address.AddressLine1}}</td> <td>{ ...

Having trouble with Vue Router view not functioning properly in my Laravel Blade page

While diving into the world of Vue.js, I encountered a perplexing issue. After successfully running ExampleComponent.vue in my admin panel and displaying its content, I attempted to import routes from an external file (new_route_list.js) and load them via ...

Understanding AngularJS and how to effectively pass parameters is essential for developers looking

Can anyone help me figure out how to properly pass the html element through my function while using AngularJS? It seems like this method works without AngularJS, but I'm having trouble with the "this" keyword getting confused. Does anyone know how I c ...

Eclipse - enhancing outline view by utilizing require.js define(...)

My code is structured within the define(...) function in the following format: define(['angular'], function(angular) { function foo () { console.log("Hi") ; } function foo2 () { console.log("Hi") ...

Determine whether the response originates from Express or Fastify

Is there a method to identify whether the "res" object in NodeJS, built with Javascript, corresponds to an Express or Fastify response? ...

Extracting user input from an iframe and transferring it to another frame in HTML format

Can someone advise me on how to extract values from iframe1 and transmit them to iframe2 as HTML? I am open to either JavaScript or jQuery - no preference. As a beginner in javascript, I stumbled upon some code that seems relevant. <!DOCTYPE html> ...

What is the preferred default value for a property awaiting assignment from a GET response: Undefined or Null?

Say I need to display information about a product, but first I must make a GET request to get the data and assign it to the product. I'm wondering, should the default value for product in the data() function be undefined or null, and is there a differ ...

Click the 'expand' button for additional details on every row in the table

I am facing a challenge with my HTML table where I have a lot of information to add for each row. However, displaying everything at once makes the page look cluttered. Therefore, I am looking to add a "view more" button in another column for each row. Des ...

Can a feature be added based on whether or not the user has installed a specific package (optionalFeature)?

I'm developing a module and I am looking to implement a feature where if a user has installed react-intl in their project, an advanced component with translation capabilities will be exported. This approach would eliminate the need for me to maintain ...

I encountered a Node.js 203 error specifically on my computer - could this be linked to a specific environment and is there a way to resolve it

Let me explain what happened: I was working on a Nodejs-express-angular example by Brian Ford the other day, and everything was running smoothly. update:----------------this part of problem has been solved---------- However, after a few hours (during wh ...

Running "vue ui" with Node.js v17.2.0 - A step-by-step guide

After updating to Node.js v17.2.0, I am facing issues with running "vue ui" in my project. The error message I receive indicates a problem with node modules: at Object.readdirSync (node:fs:1390:3) at exports.readdir (/usr/local/lib/node_modules/@vu ...

The body parser is preventing the NODE from loading on localhost

var express = require('express'); var app = express(); var bodyParser = require('body-parser'); //ISSUE LINE **app.use(parser.json);** /////////////// var todos = []; var nextTodoItem = 1; app.use(bodyParser.json); ap ...

Preventing memory leaks by harnessing the power of Node Streams and promises

I am trying to wrap node streams in an async function, but I'm concerned about potential memory leaks in the following code. Will readStream and result be properly garbage collected after the promise is resolved or rejected? If not, what steps can I t ...

Tips on retrieving the API response using AJAX

Currently, I am attempting to retrieve the API response from Flickr using Ajax in my application built with Laravel. To accomplish this, I have established a specific Route and function dedicated to handling API calls. //Route.php Route::post('/getlo ...