Sorry to say but all client-side code can be copied.
Your best bet is to stop publishing your site online.
Obfuscate
However, there are tools that help you obfuscate code. Here’s one.
http://www.javascriptobfuscator.com/
Minify
On the other hand, most techniques employ that minify your code.
Here’s two links:
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solved Prevent copying Site Templates [closed]