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lodash源码分析之reduce #135

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HeftyKoo opened this issue Mar 21, 2020 · 0 comments
Open

lodash源码分析之reduce #135

HeftyKoo opened this issue Mar 21, 2020 · 0 comments
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api 暴露出来的接口 系列文章

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@HeftyKoo
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本文为读 lodash 源码的第一百三十四篇,后续文章会更新到这个仓库中,欢迎 star:pocket-lodash

gitbook也会同步仓库的更新,gitbook地址:pocket-lodash

依赖

import arrayReduce from './.internal/arrayReduce.js'
import baseEach from './.internal/baseEach.js'
import baseReduce from './.internal/baseReduce.js'

《lodash源码分析之arrayReduce》
《lodash源码分析之baseEach》
《lodash源码分析之baseReduce》

源码分析

reduce 的方法和数组的 reduce 方法签名一致,lodashreduce 方法除了支持数组外,还支持对象。

源码如下:

function reduce(collection, iteratee, accumulator) {
  const func = Array.isArray(collection) ? arrayReduce : baseReduce
  const initAccum = arguments.length < 3
  return func(collection, iteratee, accumulator, initAccum, baseEach)
}

先判断传入的 collection 是不是数组,如果是数组使用 arrayReduce ,否则使用 baseReduce 方法。

数组的 reduce 方法的第二个参数为初始值,这里对应的是第三个参数 accumulator

所以使用 arguments.length < 3 来判断有没有传第三个参数,如果有传,则表示有传初始值,initAccumtrue

最后调用对应的 func ,将参数传入即可。

License

署名-非商业性使用-禁止演绎 4.0 国际 (CC BY-NC-ND 4.0)

最后,所有文章都会同步发送到微信公众号上,欢迎关注,欢迎提意见:

作者:对角另一面

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