var content = UE.getEditor('myEditor').getContent();

<textarea name="myEditor" id="myEditor"></textarea>
<script type="text/javascript">
var editor = new UE.ui.Editor();
editor.render("appendInput");
//1.2.4以后可以使用一下代碼實例化編輯器
//UE.getEditor('myEditor')
</script>