I have a page that displays an error div with a class of 'validation-errors' if the user enters an incorrect value into a textbox.

Is there a way to execute a javascript function (it adds a CSS property to a button) when the error div is displayed? The function is currently called in window.onload.

Is there a way to execute the javascript function if window has changed / element added?

I have a page that displays an error div with a class of 'validation-errors' if the user enters an incorrect value into a textbox.

Is there a way to execute a javascript function (it adds a CSS property to a button) when the error div is displayed? The function is currently called in window.onload.

Is there a way to execute the javascript function if window has changed / element added?

• javascript
• jquery
• html
• css
• asp-mvc

Share Follow edited Sep 19, 2012 at 12:18 Danil Speransky 30.5k66 gold badges6969 silver badges7878 bronze badges asked Sep 19, 2012 at 11:56 TheomaxTheomax 6,8101515 gold badges5555 silver badges7373 bronze badges 5

• 1 Have you considered using JQuery to do this? – Liam Commented Sep 19, 2012 at 11:59
• Yes, but I'm not sure how I would do that. It's an MVC website, and I don't actually know/understand how the validation message is being displayed - if I did, I could add a call to the function to apply the CSS to the button when the error div/message is displayed. The button basically needs to be updated when this error message is displayed. – Theomax Commented Sep 19, 2012 at 12:02
• Here's a basic introduction to JQuery: docs.jquery./How_jQuery_Works. It's basically a JavaScript library that allows you to, among other things, select elements based on the class, id, etc. and trigger events. – Liam Commented Sep 19, 2012 at 12:05
• @Liam - Thanks, I can see already it's better than Javascript – Theomax Commented Sep 19, 2012 at 12:08
• @aspdotnetuser If you just write the CSS-rules in your stylesheet they will apply even to nodes added with AJAX. – 11684 Commented Sep 20, 2012 at 19:59

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3 Answers 3

Sorted by: Reset to default 4

$('.validation-errors').bind('DOMSubtreeModified', function () {
  if ($('.validation-errors').length) { 
    // code
  }
});

If you have jQuery on the page:

if ($('.validation-errors').length){ /*your code here */ }

in pure JS it would be something like this:

if (document.getElementsByClassName("validation-errors").length){ /*your code here */ }

if you can use jQuery, you can do

$(".validation-errors").live(function() {/* do whatever you want when your error div exists */ });