CODEWITHSUNDEEP
javascriptpromisees6-promise
Skywalker
Skywalker

Reputation: 5194

Run Promises in Sequence

My Sequence is:

(Please note I am using the Dropbox API v2)

My Code:

I am using request-promise-native library. 

let upload = (req,res) => {

let options = {
    method: 'POST',
    uri: 'https://content.dropboxapi.com/2/files/upload',
    headers: {
        'Authorization': 'Bearer Token here',
        'Dropbox-API-Arg': "{\"path\": \"/test/"+req.file.originalname+"\",\"mode\": \"overwrite\",\"autorename\": true,\"mute\": false}",
        'Content-Type': 'application/octet-stream'
    },body: fs.createReadStream(`uploads/${req.file.originalname}`)
};

rp(options)
    .then(() => {return _deleteLocalFile(req.file.originalname)})
    .then(() => {return _generateShareableLink(req.file.originalname)}) // This makes a POST request to the Dropbox API and should return a link.
    .then((shareableLink) => {sendJsonResponse(res, 200, shareableLink)})
    .catch(function (err) {sendJsonResponse(res, 500, err)});
};

From my understanding (correct me if Im wrong) promises run in parallel and return a value overtime (whichever promise resolves first). How can I run promises in a specific sequence? Is my implementation of promises within best practices?

Upvotes: 1

Views: 132

Answers (1)

Suren Srapyan
Suren Srapyan

Reputation: 68655

Your promises will work in sequence if they are used in chain. I can suggest you also to use ES8 async/await features to get more beautiful code

let upload = async (req,res) => {

   let options = {
       method: 'POST',
       uri: 'https://content.dropboxapi.com/2/files/upload',
       headers: {
        'Authorization': 'Bearer Token here',
        'Dropbox-API-Arg': "{\"path\": \"/test/"+req.file.originalname+"\",\"mode\": \"overwrite\",\"autorename\": true,\"mute\": false}",
        'Content-Type': 'application/octet-stream'
       },body: fs.createReadStream(`uploads/${req.file.originalname}`)
   };

   try {
      const request = await rp(options);
      const dlf = await _deleteLocalFile(req.file.originalname);
      const shareableLink= await _generateShareableLink(req.file.originalname);
      const sendedResponse = await sendJsonResponse(res, 200, shareableLink);
   } catch(e) {
      await sendJsonResponse(res, 500, err);
   }

}

Upvotes: 1

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