Whats my proficiency - 5 levels

proficiency-5-levels.js

function whatsMyLevel(scale) {
  let map = new Map();
  map.set('beginner', '0-20');
  map.set('familier', '21-50');
  map.set('familier', '51-50');
  map.set('expert', '71-90');
  map.set('guru', '91-99');

  let level = "god";
  map.forEach( (value, key, map) => {
    let range = value.split("-");
    if(scale >= parseInt(range[0], 10) && scale <= parseInt(range[1], 10)) {
      level = key;
    }
  });
  return 'You are ' + level;
}

// 1. Code RUN automatically: type your name
console.log(whatsMyLevel(10));