docs: function commonPrefixOf (a, b) { // eslint-disable-line id-length
    const minLen = Math.min(a.length, b.length)
    let i = 0
    for (; i < minLen; ++i) {
      if (a[i] !== b[i]) {
        break
      }
    }
    return a.substring(0, i)
  }