How to prevent execution of serverside function using javascript?

Question

I am trying to test for a textbox value.

If the value matches my criteria do a javascript function

ELSE

do textchanged event in code behind.

I have a jquery function that is triggered using javascript on change

JAVASCRIPT

function test() {
  if ($('#<%= txt.ClientID%>').val() == '1') {
      return false;
    }
};

ASP.NET

<asp:TextBox ID="txt" runat="Server" AutoPostBack="true" onchange="test(this)" />

VB.NET

Protected Sub txt_TextChanged(sender As Object, e As EventArgs) Handles txt.TextChanged
...
End Sub

While debugging the function clearly returns false however the textchanged event still causes a postback.

THE MARKUP RENDERS AS

onchange="test(this);setTimeout('__doPostBack(\'ctl00$ctl00$ctl00$Master$Content$txt\',\'\')', 0)"

QUESTION

How can the textchanged event be restricted to only execute when certain client side criteria are met?

ramby · Accepted Answer · 2014-07-16 14:32:06Z

2

try to return false inline of textbox as below:-

function test() {
    if ($('#<%= txt.ClientID%>').val() == '1') {
        return false;
    }
    return true;
};


<asp:TextBox ID="txt" runat="Server" AutoPostBack="true" onchange="if(!test(this)) return false;" />

answered Jul 16, 2014 at 14:32

ramby

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2 Comments

DreamTeK Over a year ago

Your a genius ramby, this seems to have set me along the right track. I have been scratching my head on this one for a while. Any chance your could explain why this would work and my code will not? I am really intreagued.

ramby Over a year ago

return true/false in the js function is used to exit from the js function with value true/false so as per your code you can interpret onchange="false" which does not mean to stop the postback. but on the same place if you make it onchange="return false" then it will stop the postback. so you can also avoid postback like onchange="return test();"

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How to prevent execution of serverside function using javascript?

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How can the textchanged event be restricted to only execute when certain client side criteria are met?

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