Return a promise in a node.js module

Question

I want to return the data once it has been processed by convertToHtml, but it just return the data before the converting process is over. Any suggestions on how to implement it?

exports.extractData = async function(path) {
    var mammoth = require("mammoth");
     return await mammoth.convertToHtml({path: path}, options)
            .then(function(result) {
                var html = result.value; 
                var messages = result.messages; 
                return html;
    }
}

Based on the suggestion I changed to:

exports.extractData = async function(path) {
    var mammoth = require("mammoth");
     const aux = await mammoth.convertToHtml({path: path}, options);
     return aux.value;
    }
}

Yet, I am getting:

Promise { <pending> }

I call the module like this:

var x = require("./index");
console.log(x.extractWord('docx'));

How can I obtain the result?

Thanks

Remove the `.then` part. The `async/await` already does that — kmp, Feb 15 '22 at 23:38

Nicholas Carey · Accepted Answer · 2022-02-17T21:12:41.563

Any async function returns a promise: you need to await your async function, something like this:

Give your module:

const mammoth = require("mammoth");

exports.extractData = async function(path) {

  const aux = await mammoth.convertToHtml({path: path}, options);

  return aux.value;
}

You can then say something like this:

const {extractData} = require('whatever-my-module-name-is');

async function main() {
  const extractedData = await extractData();

  process( extractedData ) ;
  
}

main()
.then( () => process.exit(0) )
.catch( err => {
  console.error(err);
  process.exit(1);
});

Farid Ghaderi · Answer 2 · 2022-02-16T00:02:43.650

0

You don't need .then when you are using async/await. async/await is just a neat replacement for promises, you shouldn't use them together

exports.extractData = async function(path) {
    var mammoth = require("mammoth");
     return await mammoth.convertToHtml({path: path}, options);
}

edited Feb 16 '22 at 00:02

answered Feb 15 '22 at 23:42

Farid Ghaderi

99
1
8

I [thought](https://jakearchibald.com/2017/await-vs-return-vs-return-await/) that using `return await` was redundant outside of try/catch and you would normally just use `return` but allegedly it's needed if you want to have useful async stack traces. – jarmod Feb 15 '22 at 23:46
I followed your instructions and I am instantiating the module from another file as var x = require(./index'); console.log(x.extractWord() and I am getting Promise { }. How can I obtain the result.html that I was getting using then(). Thanks – Gonzalo Feb 16 '22 at 00:19
I just updated the code. – Gonzalo Feb 16 '22 at 00:55

Return a promise in a node.js module

2 Answers2