I generate a dropdownList dynamicly with jquery Ajax , generated dropdown's id
is specificationAttribute . I want create add event for new tag was generated (specificationAttribute) , to do this I created Belowe script in window.load:
$(document).on('change', '#specificationattribute', function () {
    alert("Clicked Me !");
});
but it does not work . 
I try any way more like click , live but I cant any result.
jsfiddle
Code from fiddle:
$(window).load(function () {
  $("#specificationCategory").change(function () {
        var selected = $(this).find(":selected");
        if (selected.val().trim().length == 0) {
            ShowMessage('please selecet ...', 'information');
        }
        else {
            var categoryId = selected.val();
            var url = $('#url').data('loadspecificationattributes');
            $.ajax({
                url: url,
                data: { categoryId: categoryId, controlId: 'specificationattribute' },
                type: 'POST',
                success: function (data) {
                    $('#specificationattributes').html(data);
                },
                error: function (response) {
                    alert(response.error);
                }
            });
        }
    });
    $(document).on('change', '#specificationAttribute', function () {
        alert("changed ");
    });
    }
                Your fiddle has syntax errors. Since a dropdownlist generates a select, let's use one.
For my answer I used THIS HTML, more on this later: things did not match in your code
<select id="specificationAttribute" name="specificationAttribute">
</select>
Code updated: (see inline comments, some are suggestions, some errors)
$(window).on('load', function() {
  $("#specificationCategory").on('change',function() {
    var selected = $(this).find(":selected");
    // if there is a selection, this should have a length so use that
    // old:  if (selected.val().trim().length == 0) {
    if (!selected.length) { // new
    // NO clue what this is and not on the fiddle so commented it out
    //  ShowMessage('please selecet ...', 'information');
      alert("select something a category");// lots of ways to do this
    } else {
      var categoryId = selected.val();
      var url = $('#url').data('loadspecificationattributes');
      $.ajax({
        url: url,
        data: {
          categoryId: categoryId,
          controlId: 'specificationattribute'
        },
        type: 'POST',
        success: function(data) {
           // THIS line id does not match my choice of specificationAttribute so I changed it
          $('#specificationAttribute').html(data);
        },
        error: function(response) {
          alert(response.error);
        }
      });
    }
  });
  // THIS should work with the markup I put as an example
  $(document).on('change', '#specificationAttribute', function() {
    alert("changed ");
  });
});// THIS line was missing parts
                        @Uthman, it might be the case that you have given different id to select and using wrong id in onchange event as i observed in the jsfiddle link https://jsfiddle.net/a65m11b3/4/`
success: function (data) {
        $('#specificationattributes').html(data);
        },and  $(document).on('change', '#specificationAttribute', function () {
        alert("changed ");
    });  $(document).on('change', '#specificationAttribute', function () {
    alert("changed ");
});.
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