jQuery(event): watch element style

Question

let say have element like this

<div class="watch-me" style="display: none;">Watch Me Please</div>

as we can see the element above style is display: none, how can i make script to watch this element. when that element style is change to display: block then there is some code will be trigger.

many thanks...

Answer 1

As far as I know, the only way to do this would be with a timer.

I created a small jQuery plugin (yes, right here, right now) that does this against a jQuery set:

EDIT this plugin is now on GitHub: https://github.com/jacobrelkin/jquery-watcher

$.fn.watch = function(property, callback) {
   return $(this).each(function() {
       var self = this;
       var old_property_val = this[property];
       var timer;

       function watch() {
          if($(self).data(property + '-watch-abort') == true) {
             timer = clearInterval(timer);
             $(self).data(property + '-watch-abort', null);
             return;
          }

          if(self[property] != old_property_val) {
             old_property_val = self[property];
             callback.call(self);
          }
       }
       timer = setInterval(watch, 700);
   });
};

$.fn.unwatch = function(property) {
   return $(this).each(function() {
       $(this).data(property + '-watch-abort', true);
   });
};

Usage:

$('.watch-me').watch('style', function() {
   //"this" in this scope will reference the object on which the property changed
   if($(this).css('display') == 'block') { 
       //do something...
   }
});

To clear this property watcher:

$('.watch-me').unwatch('style');

Answer 2

You may use object.watch function however its non standard, there is already a cross-browser implementation Object.watch() for all browsers?

$('.watch-me').get(0).watch('style', handlerFunction);

Answer 3

function startPolling()
{
    var handle = window.setInterval(function(){

        var element = $(".watch-me");
        if (element.css("display") == "block") {
            // trigger the event
            window.clearInterval(handle);
        }

    }, 100);
}

When you want to start watching simply write:

startPolling();