Unicode aware reverse string Benchmarks

reverse-string.js

'use strict';

// run:
// node --expose-gc reverse-string.js
/*
  node v11.3.0, MacBook Late 2013

  Bench results:

  [Naive reverse string]
  memory: 93.91888427734375 MiB
  time: 3.484208316 sec

  [Unicode-Aware reverse string]
  memory: 40.07898712158203 MiB
  time: 0.41119796200000003 sec
*/

const symbols = /([\0-\u02FF\u0370-\u1DBF\u1E00-\u20CF\u2100-\uD7FF\uDC00-\uFE1F\uFE30-\uFFFF]|[\uD800-\uDBFF][\uDC00-\uDFFF]|[\uD800-\uDBFF])([\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uFE20-\uFE2F]+)/g;
const surrogates = /([\uD800-\uDBFF])([\uDC00-\uDFFF])/g;
const fromCharCode = String.fromCharCode;

function reverse(str) {
  str = str
    .replace(symbols, ($0, $1, $2) => reverse($2) + $1)
    .replace(surrogates, '$2$1');
  const len = str.length;
  const res = new Uint16Array(len);
  for (let i = 0; i < len; ++i) {
    res[len - i - 1] = str.charCodeAt(i);
  }
  let chunk = 2048, i = 0, output = '';
  while (i < len) {
    output += fromCharCode.apply(String, res.subarray(i, i + chunk));
    i += chunk;
  }
  return output;
}

function reverseNaive(s) {
  return s.split('').reverse().join('');
}

console.log('naive reverse string1:', reverseNaive('mañana'));
console.log('naive reverse string2:', reverseNaive('foo 𝌆 bar'));

console.log('reverse string1:', reverse('mañana'));
console.log('reverse string2:', reverse('foo 𝌆 bar'));
console.log('');

const base = require('crypto').randomBytes(2e5).toString();

function bench(name, callback) {
  global.gc && global.gc();

  const m0 = process.memoryUsage().heapUsed;
  const t0 = process.hrtime();

  const arr = [];
  for (let i = 0; i < 100; ++i) {
    arr.push(callback(`${i}${base}${i}`));
  }

  const t1 = process.hrtime(t0);
  const m1 = process.memoryUsage().heapUsed;

  console.log(`[${name}]`);
  console.log(`memory: ${((m1 - m0) / 2 ** 20)} MiB\ntime: ${(t1[0] + t1[1] * 1e-9)} sec\n`);
}

bench('Naive reverse string', str => reverseNaive(str));
bench('Unicode-Aware reverse string', str => reverse(str));