求帮忙解释一下 lodash源码中的 _.baseUniq 方法

好奇心促使下看了 lodash 的数组去重方法 _.uniq 的源码,它又指向了_.baseUniq,源码如下:

function baseUniq(array, iteratee, comparator) {
  let index = -1
  let includes = arrayIncludes
  let isCommon = true

  const { length } = array
  const result = []
  let seen = result

  if (comparator) {
    isCommon = false
    includes = arrayIncludesWith
  }
  else if (length >= LARGE_ARRAY_SIZE) {
    const set = iteratee ? null : createSet(array)
    if (set) {
      return setToArray(set)
    }
    isCommon = false
    includes = cacheHas
    seen = new SetCache
  }
  else {
    seen = iteratee ? [] : result
  }
  outer:
  while (++index < length) {
    let value = array[index]
    const computed = iteratee ? iteratee(value) : value

    value = (comparator || value !== 0) ? value : 0
    if (isCommon && computed === computed) {
      let seenIndex = seen.length
      while (seenIndex--) {
        if (seen[seenIndex] === computed) {
          continue outer
        }
      }
      if (iteratee) {
        seen.push(computed)
      }
      result.push(value)
    }
    else if (!includes(seen, computed, comparator)) {
      if (seen !== result) {
        seen.push(computed)
      }
      result.push(value)
    }
  }
  return result
}

里面的干扰项略多,感觉被绕晕了,求大神帮忙出个缩略版的,并解释一下思路。

baseUniq 的源码地址:链接描述

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    2 个回答
    • 11.5k

    你是从 uniq 看过去的话 代码就是只传了array没有传iteratee,comparator

    开始判断一下数组的长度如果超出 200, 就直接返回 array -> set -> array
    然后进行了一个判断 value === value,乍一看会以为怎么样都会返回 true,这个判断是为了过滤 NaN 的情况,因为 const value = NaN; value === value // false
    如果是NaN的情况会进入includes方法(内部会调用isNaN进行判断)

    整体就是 遍历传入数组 array ,每次循环检查当前值在 result 数组中是否存在,存在跳过,不存在 push

    function baseUniq(array) {
        let index = -1
        const { length } = array
        const result = []
    
        if (length >= 200) {
            const set = createSet(array)
            return setToArray(set)
        }
    
        outer:
        while (++index < length) {
            const value = array[index]
            if (value === value) {
                let resultIndex = result.length
                while (resultIndex--) {
                    if (result[resultIndex] === value) {
                        continue outer
                    }
                }
                result.push(value)
            } else if (!includes(seen, value)) {
                result.push(value)
            }
        }
        return result
    }
      • 5.2k

      有大神帮忙回答一下么?问题都沉底了。。。

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