1
var palindromePairs = function (words) {
2
  let wmap = new Map(),
3
    ans = [];
4
  for (let i = 0; i < words.length; i++) wmap.set(words[i], i);
5
  for (let i = 0; i < words.length; i++) {
6
    if (words[i] === "") {
7
      for (let j = 0; j < words.length; j++)
8
        if (isPal(words[j]) && j !== i) ans.push([i, j], [j, i]);
9
      continue;
10
    }
11
    let bw = words[i].split("").reverse().join("");
12
    let res = wmap.get(bw);
13
    if (res !== undefined && res !== i) ans.push([i, res]);
14
    for (let j = 1; j < bw.length; j++) {
15
      if (isPal(bw, 0, j - 1)) {
16
        let res = wmap.get(bw.slice(j));
17
        if (res !== undefined) ans.push([i, res]);
18
      }
19
      if (isPal(bw, j)) {
20
        let res = wmap.get(bw.slice(0, j));
21
        if (res !== undefined) ans.push([res, i]);
22
      }
23
    }
24
  }
25
  return ans;
26
};
27

28
const isPal = (word, i = 0, j = word.length - 1) => {
29
  while (i < j) if (word[i++] !== word[j--]) return false;
30
  return true;
31
};