My sliding window algorithm

sliding-window.js

const contains = (str, t) => {
  for (const c of t) {
    if (!str.includes(c)) {
      return false;
    }
  }
  return true;
}

const findWindows = (size, s, t) => {
  if (t.length > s.length || s.length < size) return [];
  const windows = [];
  for (let i = 0; i <= s.length - size; i++) {
    const str = s.substr(i, size);
    if (contains(str, t)) {
      windows.push(str);
    }
  }
  return windows;
}

const findAllWindows = (source, search, maxResults) => {
  const s = source, t = search, k = maxResults;
  const st = s.replace(/\s/g, '');
  const min = t.length;
  const max = st.length;
  let windows = [];
  for (let i = min; i <= max; i++) {
    if (windows.length >= k) break;
    const foundWindows = findWindows(i, st, t).filter(w => w.length > 0);
    windows = windows.concat(foundWindows);
  }
  windows.sort((a,b) => {
    return a.length < b.length;
  });
  return windows.slice(0, k);
}

jsfiddle https://jsfiddle.net/dgtq91s3/