Safe Code

I develope a HTML5 web based game. Ive written a custom plugin for it. It uses an external Javascript file which has to be included in the server install.

I export the game and upload to my server. Is my plugin code etc.. safe or can it esaily by downloaded, decompiled etc..

Can I somehow obfuscrate the external js file I use in the plugin

Your plugin code is safe as long as the user selects 'Minify script' on export. This compresses and obfuscates the code which should make it very difficult to reverse engineer.

External scripts are not minified. You can minify them yourself if you like with Google Closure Compiler.

if i put a external javascript file in a plugin folder (used in the game) will the script be minified and included in the exported html5 files automatically

No, it won't. You can make Construct 2 copy it to the export directory by adding it as a 'dependency' in plugin settings, but it won't be minified.

is there a tutorial for that?

rafhelp

See edittime.js in official facebook plugin