在node.js中使用async / await处理递归的结果

Question

I try to calculate the size of all files in a given directory plus in all sub directories. This is what I have so far:

const fs = require('fs');

if (process.argv.length < 3) {
    console.log("no argument given");
    process.exit(-1);
}

const dir = process.argv[2];
let bytes = 0;

(getSize = async dir => {
    fs.readdir (dir, (err, list) => {
        list.forEach (file => {
            fs.stat (dir + file, (err, stat) => {
                if (stat.isDirectory()) {
                    getSize(dir + file + "/");
                } else {
                    console.log(file + " [" + stat.size + "]");
                    bytes += stat.size;
                }
            });
        });
    });
})(dir);

setTimeout(() => {
    console.log(bytes + " bytes");
    console.log(bytes / 1000 + " Kbytes");
}, 500);

Is there a way to avoid the timeout in the end to wait for the result? I heard it is possible with async / await but I don't know how. I also want to keep this general asynchron approach if possible.

Answer 1

Promises are a bit easier to deal with. Thankfully, node has a promisify function to convert those callback-based functions into Promise-returning functions.

const { promisify } = require('util');
const fs = require('fs');
const readdir = promisify(fs.readdir);
const stat = promisify(fs.stat);

async function getSize(dir) {
  const files = await readdir(dir);
  const sizes = await Promise.all(files.map(async file => {
    const stats = await stat(dir + file);
    return stats.isDirectory() ? getSize(dir + file + "/") : stats.size;
  }));
  return sizes.reduce((total, size) => total + size, 0);
}

const bytes = await getSize(process.argv[2]);
console.log(bytes + " bytes");
console.log(bytes / 1000 + " Kbytes");