Is there any way to secure our functions and methods? so that our code will be secure

Answer 1

https://leonardociaccio.github.io/Cripty/cripty.html

Cripty provide some mechanism to encrypt your code

Answer 2

Here are few of the possible interpretations:

You want to protect your source code

..from being seen by people (because you have used something cool that you dont want others to copy)

..from being edited by people and redistributed as their own

..from being hacked by someone exploiting a weakness in the source

..from errors like buffer overflows, leak (source fortification)

..with the strongest possible licencing scheme

Each has a different approach based on the language you use. For instance, for C code 1,2,3 doesnt apply unless you shared the code publicly. For HTML/Javascript you can obfuscate but cant think of how you can do 1,2 and 3