for (i) vs for-of vs forEach (vs map)

_for (i) vs for-of vs forEach (vs map) .md

node.jsでforを使うとき、どのようにすると速いのか？実験してみた。

A: [0, 1, 2, …n] から x=-1+0+1+…(n-1) を作る

配列から結果となる数値の計算をすることについて、関数の作成を含めて評価を行う。

1. for(i) 直接 const有
2. for(i) 関数 const有
3. for(i) 直接 const無
4. for(i) 関数 const無
5. for-of 直接
6. for-of 関数
7. forEach 関数直接
8. forEach 関数別定義

B: [0, 1, 2, …n] から [-1, 0, 1, …(n-1)] を作る

配列から新たな配列を生成することについて、関数の作成を含めず評価を行う。

1. for(i) 直接
2. for(i) 関数
3. for-of 直接
4. for-of 関数
5. forEach 直接
6. forEach 関数
7. map 関数直接
8. map 関数別定義

for-bench-a.js

const newDate = () => new Date()

const length = 10000000
const numbers = Array.from({length}, (v, k) => k)

const howmanytimes = 12
const silent = true

const resarr = []

if (!silent) console.log(`length: ${length}`)

for (let n = 1; n <= howmanytimes; n += 1) {
  resarr.push(doit(n))
}

const fs = require('fs')
let csv = ""
resarr.forEach((arr) => {
  csv += `${arr.join(",")}\n`
})

const filename = `result.${newDate().getTime()}.csv`

fs.writeFile(filename, csv, (err) => {
  if (err) throw Error(err)
  if (!silent) console.log(`result written as ${filename}`)
  return
})

function doit(whattime) {
  if (!silent) console.log(`[[ ${whattime} ]]`)
  let x = 1
  const msarr = []
  if (!silent) console.log('\nfor(i) 直接 const有')
  {
    let $ = 0
    const startDate = newDate()

    for (let i = 0; i < numbers.length; i += 1) {
      const e = numbers[i]
      $ += e - 1
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor(i) 関数 const有')
  {
    let $ = 0
    const startDate = newDate()

    const fnc = (e) => $ += e - 1
    for (let i = 0; i < numbers.length; i += 1) {
      const e = numbers[i]
      fnc(e)
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor(i) 直接 const無')
  {
    let $ = 0
    const startDate = newDate()

    for (let i = 0; i < numbers.length; i += 1) {
      $ += numbers[i] - 1
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor(i) 関数 const無')
  {
    let $ = 0
    const startDate = newDate()

    const fnc = (e) => $ += e - 1
    for (let i = 0; i < numbers.length; i += 1) {
      fnc(numbers[i])
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor-of 直接')
  {
    let $ = 0
    const startDate = newDate()
    
    for (const e of numbers) {
      $ += e - 1
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor-of 関数')
  {
    let $ = 0
    const startDate = newDate()
    
    const fnc = (e) => $ += e - 1
    for (const e of numbers) {
      fnc()
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nforEach 関数直接')
  {
    let $ = 0
    const startDate = newDate()
    
    numbers.forEach((e) => $ += e - 1)

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor-of 関数別定義')
  {
    let $ = 0
    const startDate = newDate()
    
    const fnc = (e) => $ += e - 1
    for (const e of numbers) {
      fnc(e)
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  return msarr
}

for-bench-b.js

const newDate = () => new Date()

const length = 5000000
const numbers = Array.from({length}, (v, k) => k)

const howmanytimes = 12
const silent = true

const resarr = []

const fnc = (e, i, arr) => e - 1

if (!silent) console.log(`length: ${length}`)

for (let n = 1; n <= howmanytimes; n += 1) {
  resarr.push(doit(n))
}

const fs = require('fs')
let csv = ""
resarr.forEach((arr) => {
  csv += `${arr.join(",")}\n`
})

const filename = `result.${newDate().getTime()}.csv`

fs.writeFile(filename, csv, (err) => {
  if (err) throw Error(err)
  if (!silent) console.log(`result written as ${filename}`)
  return
})

function doit(whattime) {
  if (!silent) console.log(`[[ ${whattime} ]]`)
  let x = 1
  const msarr = []
  if (!silent) console.log('\nfor(i) 直接')
  {
    const $ = []
    const startDate = newDate()

    for (let i = 0; i < numbers.length; i += 1) {
      $.push(numbers[i] - 1)
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor(i) 関数')
  {
    const $ = []
    const startDate = newDate()

    for (let i = 0; i < numbers.length; i += 1) {
      $.push(fnc(numbers[i], i, numbers))
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor-of 直接')
  {
    const $ = []
    const startDate = newDate()
    
    for (const e of numbers) {
      $.push(e - 1)
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nfor-of 関数')
  {
    const $ = []
    const startDate = newDate()
    
    for (const e of numbers) {
      $.push(fnc(e, null, numbers))
    }

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1
  if (!silent) console.log('\nforEach 直接')
  {
    const $ = []
    const startDate = newDate()
    
    numbers.forEach((e) => $.push(e - 1))

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nforEach 関数')
  {
    const $ = []
    const startDate = newDate()
  
    numbers.forEach((e, i, arr) => $.push(fnc(e, i , arr)))

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nmap 関数直接')
  {
    const startDate = newDate()

    const $ = numbers.map((e) => e - 1)

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  if (!silent) console.log('\nmap 関数別定義')
  {
    const startDate = newDate()

    const $ = numbers.map(fnc)

    const time = newDate() - startDate
    if (!silent) console.log(`${x}: ${time}`)
    msarr.push(time)
  }
  x += 1

  return msarr
}