examples-redos-slash-ending.js

#!/usr/bin/env node

const re = /\/+$/
const batchStrings = [
  new Array(Math.pow(2, 20) + 1).join('/'),
  new Array(Math.pow(2, 18) + 1).join('/'),
  new Array(Math.pow(2, 17) + 1).join('/'),
  new Array(Math.pow(2, 16) + 1).join('/'),
  new Array(Math.pow(2, 15) + 1).join('/'),
  new Array(Math.pow(2, 14) + 1).join('/'),
  new Array(Math.pow(2, 13) + 1).join('/'),
  new Array(Math.pow(2, 12) + 1).join('/'),
  new Array(Math.pow(2, 11) + 1).join('/'),
  new Array(Math.pow(2, 10) + 1).join('/'),
  new Array(Math.pow(2, 9) + 1).join('/'),
  new Array(Math.pow(2, 8) + 1).join('/'),
  new Array(Math.pow(2, 7) + 1).join('/'),
  new Array(Math.pow(2, 6) + 1).join('/'),
  new Array(Math.pow(2, 5) + 1).join('/'),
  new Array(Math.pow(2, 4) + 1).join('/'),
  new Array(Math.pow(2, 3) + 1).join('/'),
  new Array(Math.pow(2, 2) + 1).join('/'),
  new Array(Math.pow(2, 1) + 1).join('/'),
  '/',
]

const short = '/a/b/c/'
const medium = short + (new Array(1e3)).join('/')
const long = short + (new Array(1e6)).join('/')
exports.compare = {
  redos: function() {
    return long.replace(re, '')
  },
  // endsWith_pow20: function() {
  //   let stripped = long
  //   for (const str of batchStrings) {
  //     while (stripped.endsWith(str))
  //       stripped = stripped.slice(0, -1 * str.length)
  //   }
  //   return stripped
  // },
  endsWithManual_pow20: function() {
    let stripped = long
    for (const str of batchStrings) {
      while (stripped.slice(-1 * str.length) === str)
        stripped = stripped.slice(0, -1 * str.length)
    }
    return stripped
  },
  endsWithManual_pow20_oneSlice: function() {
    let i = long.length
    for (const str of batchStrings) {
      while (i > str.length && long.substr(i - str.length, str.length) === str)
        i -= str.length
    }
    return long.substr(0, i)
  },
  //endsWith_pow10: function() {
  //  let stripped = long
  //  for (const str of batchStrings.slice(-11)) {
  //    while (stripped.endsWith(str))
  //      stripped = stripped.slice(0, -1 * str.length)
  //  }
  //  return stripped
  //},
  // endsWith_pow5: function() {
  //   let stripped = long
  //   for (const str of batchStrings.slice(-6)) {
  //     while (stripped.endsWith(str))
  //       stripped = stripped.slice(0, -1 * str.length)
  //   }
  //   return stripped
  // },
  // endsWith_pow2: function() {
  //   let stripped = long
  //   for (const str of batchStrings.slice(-3)) {
  //     while (stripped.endsWith(str))
  //       stripped = stripped.slice(0, -1 * str.length)
  //   }
  //   return stripped
  // },
  // endsWith_pow1: function() {
  //   let stripped = long
  //   for (const str of batchStrings.slice(-2)) {
  //     while (stripped.endsWith(str))
  //       stripped = stripped.slice(0, -1 * str.length)
  //   }
  //   return stripped
  // },
  //endsWith_single: function() {
  //  let stripped = long
  //  const str = '/'
  //  while (stripped.endsWith(str))
  //    stripped = stripped.slice(0, -1 * str.length)
  //  return stripped
  //},
  checkTail: function() {
    let stripped = long
    while (stripped.charAt(stripped.length - 1) === '/')
      stripped = stripped.slice(0, -1)
    return stripped
  },
  checkTail_oneSlice: function() {
    for (let i = long.length - 1; i >= 0; i--) {
      if (long.charAt(i) === '/')
        continue
      return long.slice(0, i + 1)
    }
    return ''
  },

}

const assert = require('assert')
for (const [name, fn] of Object.entries(exports.compare)) {
  assert.equal(fn(), '/a/b/c', name)
  console.error('ok', name)
}

require('../').runMain()

/*

$ node examples/redos-slash-ending.js
ok redos
ok endsWithManual_pow20
ok endsWithManual_pow20_oneSlice
ok checkTail
ok checkTail_oneSlice
benchmarking /Users/isaacs/dev/js/bench/examples/redos-slash-ending.js
Please be patient.
{
  node: '16.5.0',
  v8: '9.1.269.38-node.20',
  uv: '1.41.0',
  zlib: '1.2.11',
  brotli: '1.0.9',
  ares: '1.17.1',
  modules: '93',
  nghttp2: '1.42.0',
  napi: '8',
  llhttp: '6.0.2',
  openssl: '1.1.1k+quic',
  cldr: '39.0',
  icu: '69.1',
  tz: '2021a',
  unicode: '13.0',
  ngtcp2: '0.1.0-DEV',
  nghttp3: '0.1.0-DEV'
}
Scores: (bigger is better)

endsWithManual_pow20_oneSlice
Raw:
 > 19.66568338249754
 > 18.962075848303392
 > 19.627085377821395
 > 19.743336623889437
Average (mean) 19.499545308127942

endsWithManual_pow20
Raw:
 > 19.607843137254903
 > 18.645731108930324
 > 19.607843137254903
 > 19.64636542239686
Average (mean) 19.376945701459245

redos
Raw:
 > 1.408450704225352
 > 1.3280212483399734
 > 1.4134275618374559
 > 1.4194464158978
Average (mean) 1.3923364825751454

checkTail_oneSlice
Raw:
 > 0.47058823529411764
 > 0.4570383912248629
 > 0.4522840343735866
 > 0.44424700133274103
Average (mean) 0.45603941555632704

checkTail
Raw:
 > 0.09706853038245002
 > 0.09672115291614276
 > 0.0971534052268532
 > 0.09766578767457759
Average (mean) 0.0971522190500059

Winner: endsWithManual_pow20_oneSlice
Compared with next highest (endsWithManual_pow20), it's:
0.63% faster
1.01 times as fast
0 order(s) of magnitude faster
BASICALLY THE SAME

Compared with the slowest (checkTail), it's:
99.5% faster
200.71 times as fast
2.3 order(s) of magnitude faster

*/