lodash-part.js

var lodash = {}

lodash.chunk = chunk = (array, size = 1) => array.reduce((x, y, i) => (i % size === 0 ? x.push([y]) : x[i / size | 0].push(y), x), [])

lodash.compact = (array) => array.filter(x => x)

lodash.concat = (array, ...args) => args.reduce((x, y) => (Array.isArray(y) ? x.push(...y) : x.push(y), x), array)

lodash.difference = (array, values) => array.reduce((x, y) => (~values.indexOf(y) || x.push(y), x), [])

lodash.drop = (array, n = 1) => array.reduce((x, y, i) => (i >= n && x.push(y), x), [])

lodash.fill = (array, value, start = 0, end = array.length) => ([...array].some((x, i) => start <= i && i < end && (array[i] = value) && i >= end && true), array)

lodash.head = array => array[0]

lodash.flatten = array => array.reduce((a, b) => a.concat(b), [])

lodash.flattenDeep = array => array.reduce((a, b) => a.concat(Array.isArray(b) ? lodash.flattenDeep(b) : b), [])

lodash.flattenDepth = function flattenDepth(array, depth = 1) {
  return array.concat().reduce((a, b) => a.concat(Array.isArray(b) && depth > 1 ? flattenDepth(b, --depth) : b), [])
}

lodash.fromPairs = pairs => pairs.reduce((a, b) => (a[b[0]] = b[1], a), {})

lodash.intersection = (...arg) => arg[0].reduce((x, y) => (arg.every(a => a.includes(y)) && x.push(y), x), [])

lodash.join = (array, separator = ",") => array.reduce((a, b, i) => i === 0 ? b + "" : a + separator + b, "")

lodash.pull = (array, ...value) => [...array].reduce((x, y, i, arr) => (value.includes(y) && x.splice(i - arr.length + array.length, 1), x), array)

lodash.pullAll = (array, values) => lodash.pull(array, ...values)

lodash.reverse = array => array.reduce((x, y, i) => (i < Math.floor(array.length / 2) && ([x[i], x[array.length - 1 - i]] = [x[array.length - 1 - i], x[i]]), x), array)

//解法2： array.sort(() => 1) // 实际上这样做是不行的，取决于所用的排序算法