CODEWITHSUNDEEP
javascriptnode.js
Fede E.
Fede E.

Reputation: 1918

node async function with nested function

Currently I am trying to have an async function which has another function inside like this:

processFile: async function(req, whatTo, callback){

    const lines = [];

    const lineReader = require('readline').createInterface({
        input: require('streamifier').createReadStream(req.file.buffer)
    });

    let errorPresent = false;

    lineReader.on('line', line => {
        lines.push(line.replace(/ /g,''));
    });

    lineReader.on('close', async () => {

        try {

            const results = await Promise.map(lines, async(line) => {

                return await Transform(line);

            }, { concurrency: 80 });

            return results.join("\r\n");

        }catch(err){
            throw err;
        }

    });

}

Then I have a route, which calls this function, like this:

const data = await tokenizer.processFile(req, 'tokenize');

res.setHeader('Content-Type', 'text/plain'); 
res.setHeader('Content-Disposition', 'attachment; filename=tokenized.txt');
res.write(data, 'binary');
res.end();

The return results.join("\r\n"); isn't 'returning' the processFile.

How can I achieve this?

Upvotes: 0

Views: 76

Answers (1)

Cody Geisler
Cody Geisler

Reputation: 8617

My suggestion is to split up your conversion of line reader from cb to a promise doing something like this: 

processFile: (req, whatTo) => new Promise((res,rej)=>{

    const lines = [];

    const lineReader = require('readline').createInterface({
        input: require('streamifier').createReadStream(req.file.buffer)
    });

    let errorPresent = false;

    lineReader.on('line', line => {
        lines.push(line.replace(/ /g,''));
    });

    lineReader.on('close', function(){
      res(lines);
    });
    // UNCAUGHT ERRORS, USE rej() for others
});

Then handling your transform back in your async/await world like this:

let data;
let lines = await tokenizer.processFile(req, 'tokenize');
let results = await Promise.map(lines, async (line) => {
  return await Transform(line);
}, { concurrency: 80 });

Upvotes: 1

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