javascript-loop-performance.js

javascript-loop-performance

#!/usr/bin/env node

// Figure out how performant different looping constructs in JavaScript are.
// Sample output:

// for-of: elapsed.stats={"min":26,"max":59,"avg":33.13} elapsed=26,26,27,28,29,30,30,30,30,30,30,30,30,30,31,31,31,31,31,31,31,31,31,31,31,31,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,32,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,33,34,34,34,34,34,34,34,34,34,34,34,34,34,34,34,34,34,34,34,35,35,35,35,35,35,35,35,36,36,36,36,36,36,36,37,38,40,47,59
// forEach: elapsed.stats={"min":34,"max":77,"avg":56.53} elapsed=34,52,52,52,52,53,53,53,53,53,53,53,53,53,53,53,53,53,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,55,55,55,55,55,55,55,55,55,55,55,55,55,55,55,55,55,55,56,56,56,56,56,56,56,56,56,56,56,56,56,56,56,57,57,57,57,57,57,57,57,57,57,58,58,58,58,59,59,59,59,59,60,60,61,61,63,63,65,67,69,70,70,72,73,77
// map: elapsed.stats={"min":38,"max":76,"avg":62.48} elapsed=38,58,58,58,58,58,58,58,58,58,58,58,58,58,59,59,59,59,59,59,59,59,59,59,59,59,59,60,60,60,60,60,60,60,60,60,61,61,61,61,61,61,61,61,62,62,62,62,62,62,62,62,62,63,63,63,63,63,63,63,63,63,63,63,63,63,64,64,64,64,64,64,64,64,64,65,65,65,65,66,66,66,66,66,66,67,67,67,67,69,69,69,70,71,71,71,72,73,73,76

const LIMIT = process.env.LIMIT || 1000000
const ITERATIONS = process.env.LIMIT || 100
const data = []
for (let i = 0; i < LIMIT; ++i) data.push(i)

function min (values) {
  let result
  for (const value of values) {
    if (result === undefined || value < result) {
      result = value
    }
  }
  return result
}

function max (values) {
  let result
  for (const value of values) {
    if (result === undefined || value > result) {
      result = value
    }
  }
  return result
}

function avg (values) {
  return sum(values) / values.length
}

function sum (values) {
  return values.reduce((acc, value) => acc + value, 0)
}

function stats (values) {
  return {
    min: min(values),
    max: max(values),
    avg: avg(values),
  }
}

function logElapsed (name, fn) {
  const allElapsed = []
  for (let i = 0; i < ITERATIONS; i++) {
    const startTime = new Date()
    fn()
    const elapsed = new Date() - startTime
    allElapsed.push(elapsed)
  }
  console.log(`${name}: elapsed.stats=${JSON.stringify(stats(allElapsed))} elapsed=${allElapsed.sort()}`)
}

logElapsed('for-of', () => {
  const newData = []
  for (const i of data) {
    newData.push(i * i)
  }
})

logElapsed('forEach', () => {
  const newData = []
  data.forEach(i => {
    newData.push(i * i)
  })
})

logElapsed('map', () => {
  const newData = []
  data.map(i => {
    newData.push(i * i)
  })
})