graphql-let faster "readHash" test

test.js

import { createReadStream, existsSync, readFileSync, promises } from "fs";
import assert from 'assert'
const {readFile} = promises;

const filepath =
  '__tests__/.__fixtures/hmr/__generated__/src/viewer.graphql.tsx';

const len = 1000;
const leadingStringOfGeneratedContent = '/* ';
const hexHashLength = 40;
const expect = 'a569b0aa92ed95d91042bad57795c0af105056a3';

function readHashStream(filePath) {
  if (!existsSync(filePath)) {
    return Promise.resolve(null);
  }

  return new Promise((resolve, reject) => {
    const stream = createReadStream(filePath, {
      encoding: 'utf-8',
      highWaterMark: leadingStringOfGeneratedContent.length + hexHashLength,
    });
    stream.on('error', (error) => reject(error));
    stream.on('data', (chunk) => {
      const hash = chunk.slice(leadingStringOfGeneratedContent.length);
      if (hash.length !== hexHashLength) return resolve(null);

      resolve(hash);
    });
    stream.read();
  });
}

function readHashSync(filepath) {
  if (!existsSync(filepath)) return null;
  try {
    const content = readFileSync(filepath, 'utf-8')
    return content.slice(leadingStringOfGeneratedContent.length,
      leadingStringOfGeneratedContent.length + hexHashLength);
  } catch (err) {
  }
}


async function readHashAsync(filepath) {
  if (!existsSync(filepath)) return null;
  try {
    const content = await readFile(filepath, 'utf-8')
    return content.slice(leadingStringOfGeneratedContent.length,
      leadingStringOfGeneratedContent.length + hexHashLength);
  } catch (err) {
  }
}

async function main() {
  let v;

  console.time('Use sync');
  for (let i = 0; i < len; i++) v = readHashSync(filepath)
  console.timeEnd('Use sync');
  assert.strictEqual(v, expect);

  v = ''
  console.time('Use async');
  for (let i = 0; i < len; i++) v = await readHashAsync(filepath)
  console.timeEnd('Use async');
  assert.strictEqual(v, expect);

  v = ''
  console.time('Use stream');
  for (let i = 0; i < len; i++) v = await readHashStream(filepath)
  console.timeEnd('Use stream');
  assert.strictEqual(v, expect);
}

main();

It turned out loading the whole content synchronously is the fastest.

Use sync: 38.623ms
Use async: 468.091ms
Use stream: 8.753s