Node.js read file using async/await

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roscoe_x

I am experimenting with async/await code to read file. Here's my code:

var fs = require('fs');

function readFile(fileName) {
  return new Promise(resolve => {
    //console.log(test);
    fs.readFile(fileName, 'utf8', function (err, data) {
      if (err) throw err;

      console.log(fileName)
      console.log(data)
    })
    resolve();
  });
}

async function run() {
  await readFile('file1.txt');
  await readFile('file2.txt');
  readFile('file3.txt');
}

run();

But the result is still random. It means file3 sometime read before file2. Where am I doing wrong?

There are a couple options with native node functionality

A) With the fs.promises API

You can use destructuring assignment on import to alias fs.promises as just fs

const { promises: fs } = require("fs");

(async () => {
    try {
        let file1 = await fs.readFile("file1.txt", "utf-8");
        let file2 = await fs.readFile("file2.txt", "utf-8");

    } catch (e) {
        console.log("e", e);
    }
})()

B) With util.promisify API

const fsSync = require("fs");
const {promisify} = require("util")

const fs = {
  readdir: promisify(fsSync.readdir),
  readFile: promisify(fsSync.readFile),
  // etc
};

(async () => {
    try {
        let file1 = await fs.readFile("file1.txt", "utf-8");
        let file2 = await fs.readFile("file2.txt", "utf-8");

    } catch (e) {
        console.log("e", e);
    }
})()

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