fuzzer that mutating javascript file instead of binary file

I’m looking for a fuzzer that I can give it a number of initial seed inputs (these seed inputs are javascript files) and it mutates them. you know I’m looking for a fuzzer like afl but afl works on binary files (the inputs are binary and it mutates binary files) while I want a fuzzer that works on javascript files (the inputs are javascript files and it mutates javascript files). do you know any?