Custom Code block and JS

Wondering if there is a limitation or is it actually possible to create a block that allows the user of the editor to write custom javascript code as they are building the template? For example drag and drop a custom code block and write the javascript in it? Example: I created a link and wanted to capture the click event to make an Ajax request etc... I know it is possible to update the editors initialization code to include an external javascript file but ideally we would like this to be handled dynamically in a single place without having to edit settings every time we add a new javascript...