anigram.js

// ===============================================================
// Given two strings, write a function to determine if the second
// string is an anagram of the first. An anagram is a word, phrase
// or name formed by rearranging the letters of another, such as:
// cinema, formed from iceman.
// ===============================================================

function validAnagram(first, second) {
  // Edgecase to test whether or not both strings are of equal length.
  if (first.length !== second.length) {
    return false;
  }
  const lookup = {};
  for (let i = 0; i < first.length; i++) {
    let letter = first[i];
    // if letter exists, increment, otherwise set to 1
    lookup[letter] ? (lookup[letter] += 1) : (lookup[letter] = 1);
  }
  for (let i = 0; i < second.length; i++) {
    let letter = second[i];
    // can't find letter or letter is zero then it's not an anagram
    if (!lookup[letter]) {
      return false;
    } else {
      lookup[letter] -= 1;
    }
  }
  return true;
}

validAnagram('rat', 'car');
validAnagram('anagram', 'nagaram');