How to create object of another javascript class in nodejs

Question

Hi I want to create an object of ProfileComparator in another index.js file but I am getting an error.

strategy.js

var cosineUtils = require("./jscosine");

var ProfileComparator = function(algo, x, y, threshold) {
  this.algo = algo;
  this.x = x;
  this.y = y;
  this.threshold = threshold;
};

ProfileComparator.prototype.findMatches = function() {
  return this.algo(this.x, this.y, this.threshold);
};

var cosineAlgoStrategy = function(x, y, threshold) {
  var similarityCount = cosineUtils.cosineSimilarity(x, y);

  if (similarityCount >= threshold) {
    return y;
  }

  console.log("------------------------------------");
  console.log("cosine");
  console.log("------------------------------------");
};

var pearsonAlgoStrategy = function(x, y, threshold) {
  console.log("------------------------------------");
  console.log(threshold);
  console.log("------------------------------------");
};

I am able to create object of ProfileComparator in strategy.js not in other javascript file like below

var cosineAlgo = new ProfileComparator(cosineAlgoStrategy, "x", "y", 0.9);
return cosineAlgo.findMatches();

index.js

I am trying to do same in index.js but I am getting an error here:

var strategyUtils = require("./strategy");

function computeSimilarity(x, user) {
  var cosineAlgo = new ProfileComparator(cosineAlgoStrategy, x, y, 0.9);
  return cosineAlgo.findMatches();
}

StackTrace:

ReferenceError: ProfileComparator is not defined
    at computeSimilarity (/user_code/index.js:187:24)
    at /user_code/index.js:232:16
    at process._tickDomainCallback (internal/process/next_tick.js:135:7)

Does anyone know how to resolve it ?

You have not exported ProfileComparator from strategy.js file. — Prakash Sharma
– Prakash Sharma, Commented Sep 3, 2017 at 18:02
Use 'export' befor func name. Then it will accessible outside of local file — user2589455
– user2589455, Commented Sep 3, 2017 at 18:03

Prakash Sharma · Accepted Answer · 2017-09-03 18:06:46Z

2

You need to export your ProfileComparator comparator function from strategy.js file like this

module.exports = ProfileComparator

And in your index.js, require it like this

var ProfileComparator = require("./strategy");

answered Sep 3, 2017 at 18:06

Prakash Sharma

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1 Comment

N Sharma Over a year ago

I am getting this now

ReferenceError: cosineAlgoStrategy is not defined     at computeSimilarity (/user_code/index.js:187:42)     at /user_code/index.js:232:16     at process._tickDomainCallback (internal/process/next_tick.js:135:7)

here var cosineAlgo = new ProfileComparator(cosineAlgoStrategy, x, y, 0.9);

marpme · Accepted Answer · 2017-09-03 18:32:35Z

1

Here you go with your exported class and algorithms that you might wanna use in your Comparator:

const ProfileComparator = function(algo, x, y, threshold) {
  this.algo = algo
  this.x = x
  this.y = y
  this.threshold = threshold
}

ProfileComparator.prototype.findMatches = function() {
  return this.algo(this.x, this.y, this.threshold)
}

const cosineAlgoStrategy = function(x, y, threshold) {
  var similarityCount = cosineUtils.cosineSimilarity(x, y)

  if (similarityCount >= threshold) {
    return y
  }

  console.log('------------------------------------')
  console.log('cosine')
  console.log('------------------------------------')
}

const pearsonAlgoStrategy = function(x, y, threshold) {
  console.log('------------------------------------')
  console.log(threshold)
  console.log('------------------------------------')
}

module.exports = { ProfileComparator, cosineAlgoStrategy, pearsonAlgoStrategy }

This would be your new index.js file where you import all you needed modules:

const { ProfileComparator, cosineAlgoStrategy, pearsonAlgoStrategy } = require("./strategy");

function computeSimilarity(x, user) {
    var cosineAlgo = new ProfileComparator(cosineAlgoStrategy, x, y, 0.9);
    return cosineAlgo.findMatches();
}

edited Sep 3, 2017 at 18:32

answered Sep 3, 2017 at 18:10

marpme

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7 Comments

N Sharma Over a year ago

I am getting

TypeError: ProfileComparator is not a constructor     at computeSimilarity (/user_code/index.js:191:20)     at /user_code/index.js:236:16     at process._tickDomainCallback (internal/process/next_tick.js:135:7)

marpme Over a year ago

@Williams I corrected my code. I was just typing, what I had on my mind.

N Sharma Over a year ago

Thanks a lot :) it worked. I didn't know that we can export multiple too using this syntax

marpme Over a year ago

@Williams you are welcome. Sure you can use this 'trick', creating an export object, which you then destruct on the import side to access the functionalities more easily.

N Sharma Over a year ago

If I add var instead of const here const { ProfileComparator, cosineAlgoStrategy, pearsonAlgoStrategy } = require("./strategy"); then it won't work ?

|

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Fix

You need to export the ProfileComparator!
Add: module.exports = ProfileComparator; to the end of the strategy.js file!
Now you can require it in other files with something like this:
var ProfileComparator = require('path/to/the/module');.
Dont forget to checkout this: https://nodejs.org/docs/latest/api/modules.html#modules_module_exports

Explanation of the error

The error occurred because you tried to create a new instance of the ProfileComparator without it beeing in scope!

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Sep 3, 2017 at 18:05

C. Mürtz

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3 Comments

N Sharma Over a year ago

I am getting this now

ReferenceError: cosineAlgoStrategy is not defined at computeSimilarity (/user_code/index.js:187:42) at /user_code/index.js:232:16 at process._tickDomainCallback (internal/process/next_tick.js:135:7)

here var cosineAlgo = new ProfileComparator(cosineAlgoStrategy, x, y, 0.9);

C. Mürtz Over a year ago

Right, this variable is not in scope!

C. Mürtz Over a year ago

I will add the solution to my answer later!

user2589455 · Accepted Answer · 2017-09-03 18:07:02Z

0

Change

var ProfileComparator = function(algo, x, y, threshold) {
  this.algo = algo;
  this.x = x;
  this.y = y;
  this.threshold = threshold;
};

To

export const ProfileComparator = function(algo, x, y, threshold) {
  this.algo = algo;
  this.x = x;
  this.y = y;
  this.threshold = threshold;
};

Import as

Import { ProfileComparator } from '<file location>'

answered Sep 3, 2017 at 18:07

user2589455

1 Comment

marpme Over a year ago

not natively working in nodejs, since export/import isn't standardized, yet.

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