baseFindIndex

[jingchaocheng]

/**
 * The base implementation of `findIndex` and `findLastIndex`.
 *
 * @private
 * @param {Array} array The array to inspect.
 * @param {Function} predicate The function invoked per iteration.
 * @param {number} fromIndex The index to search from.
 * @param {boolean} [fromRight] Specify iterating from right to left.
 * @returns {number} Returns the index of the matched value, else `-1`.
 */
function baseFindIndex(array, predicate, fromIndex, fromRight) {
  // 获取 array length
  const { length } = array

  // 获取循环 index, 这个根据 fromRight 判断 fromIndex 是 +1 还是 -1
  // 在下面循环中会 index-- 和 ++index 会去去除掉
  let index = fromIndex + (fromRight ? 1 : -1)

  // 循环
  while ((fromRight ? index-- : ++index < length)) {
    // 如果 predicate 返回 true，返回当前 index
    if (predicate(array[index], index, array)) {
      return index
    }
  }

  // predicate 没有返回 true 循环结束后返回 -1
  return -1
}

export default baseFindIndex