Making File Names Unique LeetCode solution in JavaScript

1
/**
2
 * @param {string[]} names
3
 * @return {string[]}
4
 */
5
var getFolderNames = function (names) {
6
  // save existed folder names
7
  let hashMap = new Map();
8
  for (let name of names) {
9
    let finalName = name;
10
    // next smallest suffix number
11
    // if this name is not present in the map, next smallest suffix will be 1
12
    let number = hashMap.get(name) || 1;
13
    if (hashMap.has(name)) {
14
      // append suffix to original name
15
      finalName += "(" + number + ")";
16
      // find the smallest suffix that hasn't been used before
17
      while (hashMap.has(finalName)) {
18
        number++;
19
        // try to use new suffix to update name
20
        finalName = name + "(" + number + ")";
21
      }
22
      // update next smallest suffix number of new name
23
      hashMap.set(finalName, 1);
24
    }
25
    // update next smallest suffix number of original name
26
    hashMap.set(name, number);
27
  }
28
  return Array.from(hashMap.keys());
29
};