Replace file extensions recursively from *.js to *.es6

replaceExt

# Change .js and .es6 for whatever extension you like
for file in **/*.js;do mv $file $(echo ${file%*.*}.es6);done

# If wanna test it first then run
for file in **/*.js;do echo ${file%*.*}.es6;done

# Bash function, i.e. replaceExt(js, es6)
replaceExt () {

  # If new extension is void/empty
  if [ -z "$2" ]; then
      for file in **/*.$1;do mv $file $(echo ${file%*.*});done
      exit 0;
  fi
  
  for file in **/*.$1;do mv $file $(echo ${file%*.*}.$2);done
  
}