The HTML Editor has three modes: Design, HTML Text and Preview mode.
Design mode is in an IFrame. HTML Text is presented in a TextArea and the preview mode is in another Iframe. The code rendered about these three modes is as below.
<iframe id="editor1_ctl02_ctl00" name="editor1_ctl02_ctl00" marginheight="0" marginwidth="0" frameborder="0" src="javascript:false;" style="height:100%;width:100%;display:none;border-width:0px;">
/iframe>
<textarea id="editor1_ctl02_ctl01" class="ajax__htmleditor_htmlpanel_default" style="height:100%;width:100%;display:none;">
/textarea>
<iframe id="editor1_ctl02_ctl02" name="editor1_ctl02_ctl02" marginheight="0" marginwidth="0" frameborder="0" src="javascript:false;" style="height:100%;width:100%;display:none;border-width:0px;">
/iframe>
In the design mode, we can use the following JavaScript to append a callback function in onKeypress event.
<script type="text/javascript">
var count = 0;
function pageLoad() {
$get('editor1_ctl02_ctl00').contentWindow.document.body.onkeypress = function() {
count++;
$get('cc').innerHTML = "you input " + count + "charactors";
};
}
/script>
In the same way, you can append another keypress event on the TextArea and preview IFrame.