how to run embedded script when editing

I insert some javascript into what I am editing in FckEditor, such as : alert('hi')

when I write it like this:

You are using <a href="http://www.fckeditor.net/">FCKeditor</a></em><strong id="input1" onclick="alert('aaa');">HI</strong>

it works, a alert box popup when i click HI

but, when I write it like this:

You are using <a href="http://www.fckeditor.net/">FCKeditor</a></em><strong id="input1" onclick="myalert()">HI</strong>
<script>
function myalert()
{
    alert{'aaa'}
} 
</script>

It doesn't work, and the browser reports error : cannot find object myalert!

my question is, what's wrong with these code, how can i make it run when i insert some js code between <script> and </script>.

thanks for any comment