what is the use of "JavaScript Obfuscator" in ASM ?

Obfuscator changes software codes to make it very difficult to be read, e.g. changing the function and variable name to random names, removing new lines and tab with spaces. adding random codes, etc.

As it is difficult to be read, users including hackers will get more difficulties to find bugs/loopholes in the software codes.
This doesnt affect the internal web developer as they have original (non obfuscated) codes.

Obfucation example is in: https://obfuscator.io/#code

If the codes is already obfuscated, it is better to exclude it from ASM obfuscator.
I suggest you check this with the web developer team.