LeetCode: Longest String Chain Solution

1/**
2 * @param {string[]} words
3 * @return {number}
4 */
5var longestStrChain = function (words) {
6  const setWords = new Set(words)
7  const memo = {}
8
9  const recursion = word => {
10    if (memo[word] !== undefined) return memo[word]
11    if (setWords.has(word) === false) return 0
12
13    let max = -Infinity
14    for (let i = 0; i < word.length; i++) {
15      max = Math.max(
16        max,
17        1 + recursion(word.substring(0, i) + word.substring(i + 1))
18      )
19    }
20
21    return (memo[word] = max)
22  }
23
24  return Math.max.apply(null, words.map(recursion))
25}