Valid Anagram

Problem statement

Given two strings s and t, return true if t is an anagram of s, and false otherwise.

An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.

Example 1:

Input: s = "anagram", t = "nagaram"Output: true

Example 2:

Input: s = "rat", t = "car"Output: false

Constraints:

• 1 <= s.length, t.length <= 5 * 104
• s and t consist of lowercase English letters.

Follow up: What if the inputs contain Unicode characters? How would you adapt your solution to such a case?

My solution

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isAnagram = function(s, t) {
  if (s.length !== t.length) {
      return false;
  }
    
    const map = {};
    for (const char of s.split("")) {
        if (!map[char]) {
            map[char] = 0
        }
        ++map[char]
    }
    
    for (const char of t.split("")) {
        if (!map[char]) {
            map[char] = 0
        }
        --map[char]
    }
    
    return Object.keys(map).filter(v => map[v] !== 0).length === 0
};