Problem with ParticleJS and Node asynchronicity

[nrobinson2000]

Already posted this on Slack, but here goes. I am learning Node and trying to use ParticleJS. When using the example code from https://docs.particle.io/reference/javascript/, it tries to list devices before the access token has been obtained. I’m still getting used to the asynchronicity of Node.

var Particle = require('particle-api-js');
var particle = new Particle();
var token;

particle.login({username: 'email', password:
'pass'}).then(
  function(data) {
    token = data.body.access_token;
    console.log('Got token!');
  },
  function (err) {
    console.log('Could not log in.', err);
  }
);


var devicesPr = particle.listDevices({ auth: token });

devicesPr.then(
  function(devices){
    console.log('Devices: ', devices);
  },
  function(err) {
    console.log('List devices call failed: ', err);
  }
);

Output:

List devices call failed:  { Error: HTTP error 400 from https://api.particle.io/v1/devices - The access token was not found
    at /Users/nrobinson/test/node_modules/particle-api-js/lib/Agent.js:184:19
    at Request.callback (/Users/nrobinson/test/node_modules/superagent/lib/node/index.js:631:3)
    at /Users/nrobinson/test/node_modules/superagent/lib/node/index.js:795:18
    at IncomingMessage.<anonymous> (/Users/nrobinson/test/node_modules/superagent/lib/node/parsers/json.js:16:7)
    at emitNone (events.js:91:20)
    at IncomingMessage.emit (events.js:185:7)
    at endReadableNT (_stream_readable.js:974:12)
    at _combinedTickCallback (internal/process/next_tick.js:74:11)
    at process._tickCallback (internal/process/next_tick.js:98:9)
  statusCode: 400,
  errorDescription: 'HTTP error 400 from https://api.particle.io/v1/devices - The access token was not found',
  shortErrorDescription: 'The access token was not found',
  error:
   { Error: Bad Request
       at Request.callback (/Users/nrobinson/test/node_modules/superagent/lib/node/index.js:626:17)
       at /Users/nrobinson/test/node_modules/superagent/lib/node/index.js:795:18
       at IncomingMessage.<anonymous> (/Users/nrobinson/test/node_modules/superagent/lib/node/parsers/json.js:16:7)
       at emitNone (events.js:91:20)
       at IncomingMessage.emit (events.js:185:7)
       at endReadableNT (_stream_readable.js:974:12)
       at _combinedTickCallback (internal/process/next_tick.js:74:11)
       at process._tickCallback (internal/process/next_tick.js:98:9)
     original: null,
     response:
      Response {
        domain: null,
        _events: {},
        _eventsCount: 0,
        _maxListeners: undefined,
        res: [Object],
        request: [Object],
        req: [Object],
        links: {},
        text: '{"error":"invalid_request","error_description":"The access token was not found"}',
        body: [Object],
        files: undefined,
        buffered: true,
        headers: [Object],
        header: [Object],
        statusCode: 400,
        status: 400,
        statusType: 4,
        info: false,
        ok: false,
        redirect: false,
        clientError: true,
        serverError: false,
        error: [Object],
        accepted: false,
        noContent: false,
        badRequest: true,
        unauthorized: false,
        notAcceptable: false,
        forbidden: false,
        notFound: false,
        charset: 'utf-8',
        type: 'application/json',
        setEncoding: [Function: bound ],
        redirects: [] },
     status: 400 },
  body:
   { error: 'invalid_request',
     error_description: 'The access token was not found' } }
Got token!

[Moors7]

You can make the device list call within the return from the login. Though that works, that will quickly have you ending up in a ‘callback hell’. Instead, try googling around a bit for promises. They’re a bit abstract at first, but make some more sense when you get to know them better, and they’re much more suitable for situations like these

[BulldogLowell]

perhaps an easier way to look at Promises is to compartmentalize them into chain-able functions.

build individual functions that return a promise:

function myFirstEvent(){
  return new Promise((resolve, reject) => {
    //function here 
    if(error) reject(error);
    if(something) resolve(some args);
    else resolve(some args);
  )};
}

then chain your promises:

myFirstEvent()
.then(mySecondEvent)
.then(well, you get it)
.catch(function(reason) {
   // rejection and error handling
});

[nrobinson2000]

How would I make something like this with the code above?

[BulldogLowell]

I suppose you are not using OAuth, rather simply logging in with your account credentials… yes?

[nrobinson2000]

At the moment, yes. There also appears to be many syntax issues with myFirstEvent, according to JSHint:

function myFirstEvent(){
  return new Promise((resolve, reject) => {

    //function here 

    if(error) reject(error);
    if(something) resolve(args);
    else resolve(args);
  )};
}

[BulldogLowell]

@nrobinson2000

particle.listDevices({ auth: token });

so, although there is a JS api, we didn't really use any of the JS wrapper, rather we simply used the RESTful methods using request.

Since Particle.login returns a promise and passes data and err.

so I would start with:

function loginToAccount(credentials) {
    return new Promise((resolve, reject) => {
        Particle.login(credentials).then(
            (data) => {
                resolve(data.body.access_token);
            },
            (error) => {
                reject(error);
            });
    });
}

so...

loginToAccount(credentials)
.then(devicesPr)
.then(function(devices){
    console.log('Devices: ', devices);
  },
  function(err) {
    console.log('List devices call failed: ', err);
  }
);

no promises that it will work!

excuse the pun!

[BulldogLowell]

@nrobinson2000,

here is the function tested OK:

var Particle = require('particle-api-js');
var particle = new Particle();

let credentials = { username: 'email@email.com', password:'password'};

function getAccessToken(credentials) {
  console.log("loginToAccount()");
  return new Promise((resolve, reject) => {
    particle.login(credentials).then(
      (data) => {
        console.log(`retrieved access token:${data.body.access_token}`);
        resolve(data.body.access_token);
      },
      (err) => {
        reject(err);
      });
    });
}

function getDeviceList(token) {
  console.log("getDeviceList()");
  return new Promise((resolve, reject) => {
    particle.listDevices({'auth':token}).then(
      (devices) => {
        let deviceList = [];
        devices.body.forEach(function(element) {
          deviceList.push(element.id);
        });
        console.log(`You have ${devices.body.length} devices: ${deviceList}`);
        resolve();
      },
      (err) => {
        reject(err);
      });
    });
}

getAccessToken(credentials)
.then(getDeviceList)
.catch(function(err){
  console.log(err);
});

[nrobinson2000]

This works! Thanks.

[naikrovek]

NodeJS 7.6 (I think) and newer support async and await which make this mess a whole lot easier and much more clear.

So, hopefully most of us won’t have to deal with promises by themselves for much longer.