map_async_await2.js

const fs = require('fs');

const filelist = [
    'data/all1.txt',
    'data/all2.txt',
    'data/all3.txt',
    'data/all4.txt',
];

const filelength = async filename => new Promise((resolve, reject) => {
    fs.readFile(filename, (err, data) => {
        if (err) {
            reject(err);
        }
        else {
            resolve({filename, length:data.length});
        }
    });
});

const main = async function () {
    let contains = await Promise.all(filelist.map(filelength));
    console.log(contains);
};


main();