CODEWITHSUNDEEP
javascriptnode.jsmongoosepromiseasync-await
AlexZeDim
AlexZeDim

Reputation: 4352

Module exports promise result on fulfilled

Node -v 8.9.3

I got my own module, which is part of another module, like this:

module.js

function module(name) {
    request(['arr_result1', 'arr_result2', 'arr_result3'], {params, name}) //it's not actual request, I just rename it, 'name' is the same as function
        .then(response => {
            let data = [];
            data.name = response.data.arr_result1;
            data.guild = response.data.arr_result2;
            data.check_sum = 0;
            for (let i = 0; i < 3; i++) {
                data.check_sum += adler32.sum(new Buffer((response.data.arr_result3)));
            }
            return (data);
        })
        .then(data => {
            if (data.arr_result2 === undefined) {
                data.arr_result2 = 'TEST';
            } else {
                data.arr_result2 = data.arr_result2;
            }
            //other logic 
            console.log(data);
            return data;
        })
        .catch(function (error) {
            console.log(error )
        });
    }

module.exports = module;

and I'd like to import result ('data' from console.log) of this 'request-promise' to another file (like app.js) via:

app.js

const module = require("./module");

My module works fine, (console.log prints the exact data I want) but I can't access the data, from another *.js via import or require: In this case:

let data = module('name');
console.log(data);

I receive data - underfined (because request is promise and it's not yet fullfilled, am i right?)

but when I try to:

module('name').then((data=> {console.log(data)});

I have error: TypeError: Cannot read property 'then' of undefined

So what am I doing wrong and how should I rewrite it? Actually how it works, I point/define function('name'), and module provide a nessesary data via async request. and then return it to 'back' to app.js P.S.Actually I rename every variable in the code for better interpretation. In my own case it's not a single 'request' and my module have absolutely another name.

UPDATING

Yes, I have alredy tried with 

function module(name) {
    return request(['arr_result1', 'arr_result2', 'arr_result3'], {params, name})

and 'data' prints fine, but why then this code not working properly?

module('name').then(data => {
    console.log(data); //prints succesfully
    mongoose_schema-DB.create({data});
});

(node:17964) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): ValidationError: **here is validation error like there is no data at all, but console.log prints it dataset as 'ok'[DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Here is mongoose_schema-DB code:

let mongoose = require('mongoose');

mongoose.connect('mongodb://localhost/dma', { useMongoClient: true });
mongoose.Promise = global.Promise;
//schema itself
let mongoose_schema-DB= mongoose.model('mongoose_schema-DB', schema);
module.exports = mongoose_schema-DB;

or this part in Express

app.all('/item', function (req, res, next) {
   module('name').then(data => {
        mongooseDB_schema-DB.create({data});
    });
  },function (err, res) {
    if (err) return handleError(err);
    console.log(res);
  });
  next();
});

UPDATED

and the most interesting part, this code works fine, instead of simple mongooseDB_schema-DB.create({data})

module(name).then(data => {
    mongooseDB_schema-DB.create({
        field1: data.1,
        field2: data.2,
        field3: data.3,
        field4: data.4,
        field5: data.5,
        field6: data.6,
    });
});

I'm checking Express verison of it...

I just rewrite express version with callback, instead of .catch. Have no idea how, but it works fine. Thank you all @Bergi and @Keith for providing a nessasry support!

Upvotes: 0

Views: 1094

Answers (1)

Bergi
Bergi

Reputation: 664548

Yes, it's a promise and you need to wait for it using .then like you tried, but you also need to return that promise from your module function!

function module(name) {
    return request(['arr_result1', 'arr_result2', 'arr_result3'], {params, name})
//  ^^^^^^
    .then(…)
    .then(…)
    .catch(…);
}

You might also want to omit the catch and let the caller of your module handle the error, instead of receiving the undefined handler result.

Upvotes: 2

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