CODEWITHSUNDEEP
javascriptnode.js
codeBB
codeBB

Reputation: 83

Looping a function with callback and wait for result

I understand the basic concept of await, async and Promises. I tried alot of them but couldn't get the expected Result. For that reason, i ask you guys for help. Thx in advance.

I kicked all unnecessary lines of code, that you can see quickly what i want to do.

app.post('/create',  (req,res) => {

  var dataArray = [] 

  req.body.array.forEach((ele) => {

  let blobAdress = ele.link.split('/')[0];
  let extracted = ele.extracted
  let blob = `${blobAdress}/extracted-${extracted}.json`;
  const container =  'test';

  //SHOULD BE EXECUTED FOR EACH ELEMENT OF FOR LOOP  
 
  api.getTextFromBlob(container, blob,  (response, error) => {
   if (error){console.log("Error",error)}
     let jsonResponse = JSON.parse(response);
     console.log(jsonResponse)
     dataArray.push(jsonResponse) // I WANT ALL DATA FROM THE CB IN ONE ARRAY BUNDLED
     })
  })

// RUN THIS PART AFTER FOR LOOP HAS BEEN EXECUTED PROPER

console.log(dataArray) // !ASYNC JS --> DATA ARRAY IS EMPTY BECAUSE datArray IS CONSOLE.LOG BEFORE api.getText EXECTUED
})

Upvotes: 0

Views: 98

Answers (1)

Viktor Gusev
Viktor Gusev

Reputation: 685

You need to wrap you callback function into Promise object first:

var getTextFromBlobAsPromise = (container, blob) => new Promise((resolve, reject) => {
    api.getTextFromBlob(container, blob, (response, error) => {
        if (error) {
            console.log("Error", error)
            return reject(error); // depends on business
        }
        let jsonResponse = JSON.parse(response);
        console.log(jsonResponse)
        resolve(jsonResponse);
    })
})

Then you can await until all promises will resolve using Promise.all function:

app.post('/create', (req, res) => {

    var promises = [];
    req.body.array.forEach((ele) => {
        let blobAdress = ele.link.split('/')[0];
        let extracted = ele.extracted
        let blob = `${blobAdress}/extracted-${extracted}.json`;
        const container = 'test';

        //SHOULD BE EXECUTED FOR EACH ELEMENT OF FOR LOOP
        promises.push(getTextFromBlobAsPromise(container, blob))   ;
    })

    // RUN THIS PART AFTER FOR LOOP HAS BEEN EXECUTED PROPER
    Promise.all(promises).then(dataArray => {
        console.log(dataArray) // !ASYNC JS --> DATA ARRAY IS EMPTY BECAUSE datArray IS CONSOLE.LOG BEFORE api.getText EXECTUED
    })
})

Upvotes: 2

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