The function does not work synchronously, although I specified async / await

Question

I want to read all the JSON files from the data folder. I use the library https://www.npmjs.com/package/node-dir. I got a function, but it does not work synchronously. Variable replacements renders undefined.

async function giveHtml() {
    let replacements = await dir.readFiles(__dirname + '/data', { match: /.json$/ }, (err, content, next) => {
        if (err) {
            throw err
        }
        next()
    })
    console.log(replacements)
    return replacements
}

What's my mistake?

Shouldn't the content be in the 'content' variable that you get as the param in the callback function? — Franjo Pintarić, May 21 '19 at 13:50
@Franjo Pintarić Yes, it is there, but how can I get it back from the function? — MegaRoks, May 21 '19 at 13:51
@MegaRoks The 'readFiles' function of that lib does not return any files, so you can't get them the way you are trying to. Have you read the docs? — Franjo Pintarić, May 21 '19 at 13:54

score 4 · Accepted Answer · answered May 21 '19 at 13:57

4

You can only await a promise, and dir.readFiles does not return a promise.

You can either convert it to use a promise or use a module that already returns a promise.

answered May 21 '19 at 13:57

Quentin

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Note the `node-dir` module already has a `Promise`-based function. No need to convert or change modules. https://www.npmjs.com/package/node-dir#promisefiles-dir-callback- – wlh May 21 '19 at 14:01

red-X · Answer 2 · 2019-05-21T14:05:57.833

dir.readFiles does not seem to return a promise, it returns undefined so that's what you're getting in return. You can try creating your own promise like this.

function giveHtml() {
  return new Promise((resolve, reject) => {
    dir.readFiles(__dirname + '/data', { match: /.json$/ }, (err, content, next) => {
      if (err) {
        return reject(err)
      }
      // do stuff per file if you want
      next()
    }, (err, files) => {
      if (err) {
        return reject(err)
      }
      resolve(files)
    })
  })
}

score 0 · Answer 3 · edited May 21 '19 at 13:57

0

I think that your mistake is about not waiting for the response; You are returning the var replacements before the answer is given.

I'd try to call

console.log(replacements)

after your

next()

edited May 21 '19 at 13:57

federico scamuzzi

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answered May 21 '19 at 13:55

filo

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score 0 · Answer 4 · edited May 21 '19 at 13:59

0

async/await is syntactic sugar for a JavaScript Promise. await is listening for a resolved promise. In the npm package you are using, the readFiles function works with a callback, not a promise.

Use the promiseFiles function call instead: https://www.npmjs.com/package/node-dir#promisefiles-dir-callback-

edited May 21 '19 at 13:59

Quentin

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answered May 21 '19 at 13:58

wlh

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The function does not work synchronously, although I specified async / await

4 Answers4