How to get the Formatted HTML code ?

How to get the Formatted HTML code even in the SOURCE EDIT MODE with JavaScript?

For e.g, if I change the text "<strong>aaa</strong>" to "<strong>aaa</strongl78z>" or even omit the "</strong>", how can I get the restored, formatted Text of "<strong>aaa</strong>"?

I want just what happens when mode is switched to HTML mode form Source mode.

Only javascript technique needed, for I can't post a form directly.

function get(){
var oEditor = FCKeditorAPI.GetInstance('WritingArea') ;
var strContent = oEditor.GetXHTML(true);
}

Though adove has been tried , in Source mode, when get() called, "<strong>aaa</strongl78z>" can not restore to "<strong>aaa</strong>" as expected but just stay still.

I am suspicious of whether the parameter really works...

Thanks a lot.