How to determine if an anagram of a smaller string is found in a larger word

JavaScript, algorithms, strings

Here is one way to determine whether an anagram of a smaller string is found in a larger word.

subAnagramTry in REPL
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
function subAnagram(anagram, string) {
  const m = anagram.length;
  const n = string.length;
  if (m > n) return false;
  const target = anagram.split('').reduce((accum, char) => {
    if (!accum[char]) {
      accum[char] = 1;
    } else {
      accum[char] = accum[char]++;
    }
      return accum;
  },{});
  anagram.split('').forEach((char, i) => {
      const c = string[i];
      if (target[c]) target[c]--;
  });
  let discrepancy = Object.keys(target).reduce((accum, char) => accum + Math.abs(target[char]), 0);
    
    for ( let i = m; i < n; i++ ) {
        if (discrepancy === 0) {
          return true;
        } else {
          let c = string[i-m];
          if (target[c] !== undefined) {
            target[c]++;
            (target[c] > 0 && discrepancy++) || (discrepancy--);
          }
          c = string[i];
          if (target[c] !== undefined) {
            target[c]--;
            (target[c] < 0 && discrepancy++) || (discrepancy--);
          }
        }
    }
    return discrepancy === 0;
}