Getting Textbox value in Javascript

Question

I am trying to get the value of the textbox in a javascript  but its not working  Given below is the code of my test page   lt    Page Title    Language  VB  MasterPageFile    Site Master  AutoEventWireup  false  CodeFile  test3 aspx vb  Inherits  test3    gt    lt asp Content ID  Content1  ContentPlaceHolderID  HeadContent  runat  Server  gt   lt script language  javascript  gt       function GetAlert              var TestVar   document getElementById  txt model code   value          alert TestVar            lt  script gt   lt  asp Content gt   lt asp Content ID  Content2  ContentPlaceHolderID  MainContent  runat  Server  gt   lt asp TextBox ID  txt model code  runat  server   gt  lt  asp TextBox gt  lt br   gt  lt br   gt    lt input type  button  value  db Function  onclick  GetAlert      gt  lt br   gt   lt  asp Content gt    So where am i going wrong   How to get the text entered in the textbox in the javascript

User · Answer

lt script type  text javascript  gt              function MyFunction                     var FNumber   Number document getElementById  txtFirstNumber   value                   var SNumber   Number document getElementById  txtSecondNumber   value                   var Sum   FNumber   SNumber                  alert Sum                           lt  script gt            lt table class  auto-style1  gt               lt tr gt                   lt td gt FirstNaumber lt  td gt                   lt td gt                       lt asp TextBox ID  txtFirstNumber  runat  server  gt  lt  asp TextBox gt                   lt  td gt               lt  tr gt               lt tr gt                   lt td gt SecondNumber lt  td gt                   lt td gt                       lt asp TextBox ID  txtSecondNumber  runat  server  gt  lt  asp TextBox gt                   lt  td gt               lt  tr gt               lt tr gt                   lt td gt  amp nbsp  lt  td gt                   lt td gt                       lt asp TextBox ID  txtSum  runat  server  gt  lt  asp TextBox gt                   lt  td gt               lt  tr gt               lt tr gt                   lt td gt  amp nbsp  lt  td gt                   lt td gt                       lt asp Button ID  BtnSubmit  runat  server  Text  Submit  OnClientClick  MyFunction      gt                   lt  td gt               lt  tr gt           lt  table gt       lt  div gt   lt  form gt

User · Answer

The ID you are trying is an serverside   That is going to render in the browser differently   try to get the ID by watching the html in the Browser   var TestVar   document getElementById  ctl00 ContentColumn txt model code   value   this may works   Or do that ClientID method  That also works but ultimately the browser will get the same thing what i had written

User · Answer

lt script type  text javascript  runat  server  gt   public void Page Load object Sender  System EventArgs e                double rad 0 0          TextBox1 Attributes Add  Visible    False            if  TextBox1 Text                 rad   Convert ToDouble TextBox1 Text               Button1 Attributes Add  OnClick   alert    rad               lt  script gt    lt asp Button ID  Button1  runat  server  Text  Diameter               style  z-index  1  left  133px  top  181px  position  absolute    gt   lt asp TextBox ID  TextBox1  Visible  True  Text    runat  server               AutoPostBack  true               style  z-index  1  left  134px  top  133px  position  absolute   gt  lt  asp TextBox gt    use the help of this  hope it will be usefull

User · Answer

Since you have master page and your control is in content place holder  Your control id will be generated different in client side  you need to do like     var TestVar   document getElementById   lt    txt model code ClientID   gt    value    Javascript runs on client side and to get value you have to provide client id of your control

User · Answer

This is because ASP NET it changing the Id of your textbox  if you run your page  and do a view source  you will see the text box id is something like   ctl00 ContentColumn txt model code  There are a few ways round this   Use the actual control name    var TestVar   document getElementById  ctl00 ContentColumn txt model code   value   use the ClientID property within ASP script tags  document getElementById   lt    txt model code ClientID   gt    value   Or if you are running  NET 4 you can use the new ClientIdMode property  see this link for more details   http   weblogs asp net scottgu archive 2010 03 30 cleaner-html-markup-with-asp-net-4-web-forms-client-ids-vs-2010-and-net-4-0-series aspx1

User · Answer

Use   document getElementById   lt    txt model code ClientID   gt      instead of   document getElementById  txt model code      Also you can  use onClientClick instead of onClick

[javascript] Getting Textbox value in Javascript

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