const RecPermute = (soFar, rest) => {
  if (rest.length === 0) {
    console.log('result', soFar);
    console.log('\n\n');
  } else {
    for (let i = 0; i < rest.length; i++) {
      const remaining = rest.substring(0,i) + rest.substring(i+1);
      console.log('r', remaining) 
      console.log('R', rest);
      console.log('SF', soFar);
      console.log('------');
      RecPermute(soFar + rest[i], remaining);
    }
  }
};

x = 'abc';
RecPermute('', x);