compare-last-index-of-2.js

import Benchmark from 'benchmark'

const suite = new Benchmark.Suite()
const re = new RegExp([...Array(1000)].map((_, i) => `/${i}/(.*)()$`).join('|'))
const m = '/500/'.match(re)

console.log(m.length)
console.log(m.indexOf(''))

const io = Array.prototype.indexOf
const lio = Array.prototype.lastIndexOf
suite
  .add('indexOf()', () => {
    const i = m.indexOf('', 1)
    return m.length - 1 === i || m[i + 1] !== '' ? i : i + 1
  })
  .add('lastIndexOf()', () => {
    return m.lastIndexOf('')
  })
  .add('lastIndexOf by for', () => {
    for (let i = m.length - 1; i > 0; i--) {
      if (m[i] === '') {
        return i
      }
    }
    return -1
  })
  .add('lastIndexOf by while', () => {
    let i = m.length
    while (i--) {
      if (m[i] === '') {
        return i
      }
    }
    return -1
  })
  .add('Array.prototype.indexOf.call', () => {
    io.call(m, '', 1)
  })
  .add('Array.prototype.lastIndexOf.call', () => {
    lio.call(m, '')
  })
  .on('cycle', (event) => {
    console.log(String(event.target))
  })
  .on('complete', function () {
    console.log(`Fastest is ${this.filter('fastest').map('name')}`)
  })
  .run({ async: true })

Node.js v16.14.0@c5.large

indexOf() x 850,664 ops/sec ±0.37% (95 runs sampled)
lastIndexOf() x 319,252 ops/sec ±0.08% (98 runs sampled)
lastIndexOf by for x 857,151 ops/sec ±0.02% (94 runs sampled)
lastIndexOf by while x 687,093 ops/sec ±0.03% (99 runs sampled)
Array.prototype.indexOf.call x 851,614 ops/sec ±0.19% (99 runs sampled)
Array.prototype.lastIndexOf.call x 319,220 ops/sec ±0.17% (99 runs sampled)
Fastest is lastIndexOf by for

Node.js v17.5.0@c5.large

indexOf() x 1,670,325 ops/sec ±0.38% (98 runs sampled)
lastIndexOf() x 293,537 ops/sec ±0.11% (95 runs sampled)
lastIndexOf by for x 857,078 ops/sec ±0.02% (100 runs sampled)
lastIndexOf by while x 686,762 ops/sec ±0.04% (99 runs sampled)
Array.prototype.indexOf.call x 1,661,371 ops/sec ±0.27% (96 runs sampled)
Array.prototype.lastIndexOf.call x 293,507 ops/sec ±0.20% (96 runs sampled)
Fastest is indexOf()

Node.js v18.0.0-pre@i9

indexOf() x 560,852 ops/sec ±0.77% (93 runs sampled)
lastIndexOf() x 328,680 ops/sec ±1.00% (90 runs sampled)
lastIndexOf by for x 958,723 ops/sec ±0.98% (92 runs sampled)
lastIndexOf by while x 757,040 ops/sec ±1.18% (89 runs sampled)
Array.prototype.indexOf.call x 517,647 ops/sec ±0.99% (88 runs sampled)
Array.prototype.lastIndexOf.call x 328,206 ops/sec ±0.62% (91 runs sampled)
Fastest is lastIndexOf by for