<h2>Classic editor</h2>
<div id="editor">
	<p>I'm CKEditor 4 instance.</p>
</div>
<button onClick="setComboValue( 'one' )" >one</button>
<button onClick="setComboValue( 'two' )" >two</button>
<button onClick="setComboValue( 'three' )" >three</button>

<script>
	var editor = CKEDITOR.replace( 'editor', {
			toolbar: [ [ 'custom_richcombo' ] ],
			on: {
				'pluginsLoaded': function( evt ) {
					var editor = evt.editor,
						items = {
							'one': 'one',
							'two': 'two',
							'three': 'three'
						}