I'm not too sure I understand your question 100%, but I'm gonna try to answer the best I can.
If you're adding the JavaScript via Wordpress's Page/Post text editor, you have to make sure you're using the HTML editor (not visual).
That would be step 1.
Step 2 would be adding the script itself. Make sure you don't have any line breaks in between your code, or it will break (learned that from experience)
For example, this will work:
<script type="text/javascript">
var mySpecialFunction = function() {
return 'oh yeaaa';
};
mySpecialFunction();
</script>
This will not:
<script type="text/javascript">
var mySpecialFunction = function() {
return 'oh yeaaa';
};
mySpecialFunction();
</script>
At least, that's what I found with the versions of Wordpress that I'm using (dunno about their latest release)
Hope this helps!
Good luck.