Code Exercise for JS position - Wildcard Matching

wildcard-matching.js

/**
 * Validates if given string matches given pattern
 * @param {string} s - given string
 * @param {string} p - given pattern
 * @return {boolean} string matches pattern
 */
function isMatch(s, p) {
  let sIdx = 0;
  let pIdx = 0;
  
  // NOTE: set to -1 to allow for zero idx
  let pIdxPostWildcardSeq = -1;
  let sIdxPostWildcardSeq;
  
  while (sIdx < s.length) {
    // increment both idxs on character, or single-char-wildcard match
    if (pIdx < p.length && (p[pIdx] === '?' || p[pIdx] === s[sIdx])) {
      sIdx++;
      pIdx++;
    }
    // increment pattern idx on variadic wildcard
    // record both new idxs in case of preemptive mismatches on next loop
    else if (pIdx < p.length && p[pIdx] === '*') {
      pIdx++;
      
      pIdxPostWildcardSeq = pIdx;
      sIdxPostWildcardSeq = sIdx;
    }
    // if under variadic wildcard but not match:
    // - increment post wildcard idx and reset string idx to it,
    // - reset pattern idx BACK to just after wildcard
    else if (pIdxPostWildcardSeq !== -1) {
      sIdxPostWildcardSeq++;

      sIdx = sIdxPostWildcardSeq;
      pIdx = pIdxPostWildcardSeq;
    }
    // otherwise, pattern does not match -- fail!
    else {
      return false;
    }
  }
  
  // handler for extraneous, variadic wildcards
  // ex: `foobar` with `foo*r**` => true
  while (pIdx < p.length && p[pIdx] === '*') {
    pIdx++;
  }
  
  // matches if we've completely gone through all chars of pattern
  return pIdx === p.length;
};