Async/Await is only valid async func while reading a file [duplicate]

Question

I was trying to read a JSON file using Async/Await, I created my example based Native async/await approach, and I got this error.

SyntaxError: await is only valid in async function

Here is my code.

const fs = require('fs-extra');
const xml2js = require('xml2js');  
const parser = new xml2js.Parser();

const path = "file.json";

function parseJM() {
return new Promise(function (resolve, reject) {
    fs.readFile(path, { encoding: 'utf-8'}, (err, data) => {
        if (err) { reject(err); }
        else {
            resolve (parser.parseString(data.replace(/<ent_seq>[0-9]*<\/ent_seq>/g, "")
             .replace(/&(?!(?:apos|quot|[gl]t|amp);|#)/g, '')));
        }
    });
});
}

const var1 = await parseJM();
console.log(var1);

What is wrong with my code? My node version is 11.9.0, my npm version is 6.7.0 and i am using Arch Linux.

What is wrong with my code? ---> await is only valid in async function, like you've already answered in your question — baao
– baao, Commented Feb 8, 2019 at 12:36
Your using fs-extra here, so don't even bother using new Promise.. All fs methods return promises if the callback isn't passed. — Keith
– Keith, Commented Feb 8, 2019 at 12:42
The purpose of writing like this, the promise is not enough for by itself. — Kaan Taha Köken
– Kaan Taha Köken, Commented Feb 8, 2019 at 12:49
I do not understand why the heck this community so harsh on people — Kaan Taha Köken
– Kaan Taha Köken, Commented Feb 8, 2019 at 12:53

Shubham · Accepted Answer · 2019-02-11 04:01:41Z

3

You need to call await inside an async function.

(async () => {
    try {
        const var1 = await parseJM();
        console.log(var1);
    } catch (e) {
        console.error(e.message);
    }
})();

Edit: As suggested by @Nik Kyriakides

edited Feb 11, 2019 at 4:01

answered Feb 8, 2019 at 12:36

Shubham

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5 Comments

nicholaswmin Over a year ago

try/catch is a must when you do this. Otherwise you're setting yourself up for swallowed errors.

Kaan Taha Köken Over a year ago

is it possible without using IFFE's

nicholaswmin Over a year ago

@KaanTahaKöken Yes, you can use a .then/resolve since async-marked functions return a Promise.

Andrei Chernikov Over a year ago

@NikKyriakides Not exactly swallowed. You will get "unhandledRejection" if an error is thrown inside parseJM() call.

nicholaswmin Over a year ago

@Aikei True, bad choice of words.

nicholaswmin · Accepted Answer · 2019-02-08 12:49:29Z

2

The error itself is telling you exactly what the issue is. You can only await inside an async-marked function.

If that's your top-level code you can just use an async IIFE:

;(async () => {
  try {
    await doSomething()  
  } catch (err) {
    console.error(err)
  }
})()

or just then/catch it. async functions return a Promise after all:

doSomething() 
  .then(result => {
    console.log(result)
  })
  .catch(err => {
    console.error(err)
  })

edited Feb 8, 2019 at 12:49

answered Feb 8, 2019 at 12:37

nicholaswmin

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4 Comments

Nino Filiu Over a year ago

Why the ;? Is it a typo or a clever hack I didn't know about?

nicholaswmin Over a year ago

Just to make sure that you don't fall into this trap.

trincot Over a year ago

That's how code looks when you don't use semi-colons consistently. Not really my thing.

nicholaswmin Over a year ago

Apart from IIFE's I've never had to prefix anything with a ;. My take is that it's far better w/o them.

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