Given two strings, determine if they are anagrams

two-string-anagram.js

/**
 * Given 2 strings, determine if they are anagrams.
 * isAnagram(string s1, string s2) => Boolean
 *
 * @note Not a very efficient example
*/
const isAnagram = (s1="", s2="") => {
    // case 1, s1 & s2 length are zero, so true
    if (s1.length != s2.length) {
        return false;
    }
    s1 = s1.toLowerCase();
    s2 = s2.toLowerCase();

    // hashtable
    let letters = {};

    // loop s1 for characters
    for (let i=0; i < s1.length; i++) {
        let letterToInt = s1[i];
        if (!letters[letterToInt]) {
            letters[letterToInt] = 0;
        }
        letters[letterToInt]++;
    }
    // loop s2 for characters
    for (let i=0; i < s2.length; i++) {
        let letterToInt = s2[i];
        if (!letters[letterToInt]) {
            letters[letterToInt] = 0;
        }
        letters[letterToInt]--;
    }
    // loop over hashkey to find non-zeros
    // if non-zero exist, not an anagram
    for (let key in letters) {
        if (letters[key] != 0) {
            return false;
        }
    }
    return true;
}

const runner = () => {
    console.log(`"" - ""; Expects: true - Answer: ${(isAnagram("", ""))}`);
    console.log(`"A" - "A"; Expects: true - Answer: ${(isAnagram("A", "A"))}`);
    console.log(`"A" - "B"; Expects: false - Answer: ${(isAnagram("A", "B"))}`);
    console.log(`"abc" - "cba"; Expects: true - Answer: ${(isAnagram("abc", "cba"))}`);
    console.log(`"AB" - "ab"; Expects: true - Answer: ${(isAnagram("AB", "ab"))}`);
};

runner();