How to execute javascript function from code-behind but only after the page loads

Question

I've found other solution on how to executes a javascript function from code-behind. The problem is that it firing before the page loads, so I can't add logic to it.

if(result)
{
   Page.ClientScript.RegisterClientScriptBlock(typeof(Page), 
                                               "Script", "confirmPwdChange();", true);
}

On the client side

<script>
   confirmPwdChange()
   {
     alert("Password has been successfully changed.");
     //Add more logic here, after user clicks the OK button...
   }
</script>

No Jquery, if possible.

Thanks for helping.

Use RegisterStartupScript instead of RegisterClientScriptBlock. See stackoverflow.com/questions/666519/… — VDWWD
– VDWWD, Commented Oct 31, 2016 at 9:11

Sreekanth · Accepted Answer · 2016-10-31 03:47:23Z

2

You might want to include the window.onload in your script file. something like this..

StringBuilder script = new StringBuilder();
script.Append("var existingHandler = window.onload;");
script.Append("window.document.body.onload = function(){ confirmPwdChange(); if (existingHandler){ existingHandler()}}");
Page.ClientScript.RegisterClientScriptBlock(typeof(Page), 
                                           "Script", script.ToString(), true);

this ensure, your change password is called on page load and retains any other existing handlers declared already on the page.

edited Oct 31, 2016 at 3:47

answered Oct 31, 2016 at 2:05

Sreekanth

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7 Comments

Richard77 Over a year ago

I'm getting this error: Uncaught SyntaxError: Unexpected token <.

Sreekanth Over a year ago

my bad. corrected the code to not include <script> tags

Richard77 Over a year ago

Now I'm getting the error: Uncaught ReferenceError: changePassword is not defined at window.onload

Sreekanth Over a year ago

I gave as a reference method name, replace the changePassword to confirmPwdChange in the server code. updated the snipet

Richard77 Over a year ago

It executed but, the same problem as it executed before the page completely loaded. While the alert was displayed, page went blank then loaded.

|

AM Douglas · Accepted Answer · 2016-10-31 02:01:45Z

1

I think you're looking for PageRequestManager

List of PageRequestManager events

var prm = Sys.WebForms.PageRequestManager.getInstance();

// beginRequest: before postback to server
prm.add_beginRequest(BeginRequestHandler);

// endRequest: after postback to server
prm.add_endRequest(EndRequestHandler);

function BeginRequestHandler(sender, args) {
    // do stuff
}

function EndRequestHandler(sender, args) {
    // do stuff
}

answered Oct 31, 2016 at 2:01

AM Douglas

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1 Comment

Richard77 Over a year ago

Can you please show how to link this to the success/failure of the code executed in the code behind.

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