jQuery watch div

Question

Is there any way to watch, if the content within a div changes?

Let's say I have:

<div id="hello"><p>Some content here</p></div>

Which at some point 5 seconds later changes to:

<div id="hello"><ul><li>This is totally different!</li></ul></div>

How can I be notified of this via a callback or something else? I can in most cases get the javascript that's doing the inserting, to tell me. But I wanted to know if it was possible.

Answer 1

The jQuery .change() method works only for form fields.

I wrote a little jQuery plugin for you:

<!-- jQuery is required -->

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>


<!-- this is the plugin -->

<script>
  jQuery.fn.contentChange = function(callback){
    var elms = jQuery(this);
    elms.each(
      function(i){
        var elm = jQuery(this);
        elm.data("lastContents", elm.html());
        window.watchContentChange = window.watchContentChange ? window.watchContentChange : [];
        window.watchContentChange.push({"element": elm, "callback": callback});
      }
    )
    return elms;
  }
  setInterval(function(){
    if(window.watchContentChange){
      for( i in window.watchContentChange){
        if(window.watchContentChange[i].element.data("lastContents") != window.watchContentChange[i].element.html()){
          window.watchContentChange[i].callback.apply(window.watchContentChange[i].element);
          window.watchContentChange[i].element.data("lastContents", window.watchContentChange[i].element.html())
        };
      }
    }
  },500);
</script>



<!-- some divs to test it with -->

<p>Testing it:  (click on divs to change contents)</p>

<div id="a" onclick="$(this).append('i')">Hi</div>
<div id="b" onclick="$(this).append('o')">Ho</div>
<div class="c" onclick="$(this).append('y')">He</div>
<div class="c" onclick="$(this).append('w')">He</div>
<div class="c" onclick="$(this).append('a')">He</div>




<!-- this is how to actually use it -->

<script>
  function showChange(){
    var element = $(this);
    alert("it was '"+element.data("lastContents")+"' and now its '"+element.html()+"'");
  }

  $('#a').contentChange(function(){  alert("Hi!") });
  $('div#b').contentChange( showChange );
  $('.c').contentChange(function(){  alert("He he he...") });
</script>

Be aware that this watches changes in the contents of the element (html) only, not the attributes.

Answer 2

There is no native jQuery/DOM event that will fire when HTML/DOM content changes.

You could (if you are feeling particularly wasteful) do something like this:

$(function() {
  var $div = $("#hello");
  var html = $div.html();
  var checking = setInterval(function() {
    var newhtml = $div.html();
    if (html != newhtml) {
      myCallback();
      html = newhtml;
    }
  },100);

  function myCallback() {
    alert('content changed!');
    // if you only want it to fire once, uncomment the following:
    // clearInterval(checking);
  }
});

Just remember, calling .html() every 100ms is probably not the best idea for your sites performance.

jsFiddle mockup

Answer 3

Maybe, it's reasonable to monitor the source of events that amend the contents of your layer(s)? Say, a user has clicked anywhere (read, "did a click") after what the contents may had changed. So if you check the .html() after a click rather than using a loop - it might save some system resources.

Answer 4

Who/what will change this? If it's some JS you control, use that to also trigger your callback. Obviously a user cannot change this.

If you want to watch a <input> element etc, use the 'change' event. jQuery version here: http://api.jquery.com/change/