I can not get the variable of a module in the app.js file (Node.js)

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I can not get the variable of a module in the app.js file (Node.js)

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#1 by (1 votes)

1

I want to send a very simple module variable from svm (machine learning) to server app.js , I'm working with NodeJS .

This is my code:

'use strict'; 
var so = require('stringify-object'); 
var svm = require('../lib');   
var xor = [
    [[0, 0], 0],
    [[0, 1], 1],
    [[1, 0], 1],
    [[1, 1], 0] ];   
// initialize predictor 
var clf = new svm.CSVC({ kFold: 1 });   
clf.train(xor)
    .progress(function(progress){
        console.log('training progress: %d%', Math.round(progress*100));
    })
    .spread(function (model, report) {
        console.log('training report: %s\nPredictions:', so(report));
        xor.forEach(function(ex){
            var prediction = clf.predictSync(ex[0]);
            console.log('   %d XOR %d => %d', ex[0][0], ex[0][1], prediction);
        });
    });

How to send variable prediction ?

I modified it like this:

'use strict';
var so = require('stringify-object');
var svm = require('../lib');

var xor = [
    [[0, 0], 0],
    [[0, 1], 1],
    [[1, 0], 1],
    [[1, 1], 0]
];
var prediction;
// initialize predictor
var clf = new svm.CSVC({
    kFold: 1
});
clf.train(xor)
    .progress(function(progress){
        console.log('training progress: %d%', Math.round(progress*100));
    })
    .spread(function (model, report) {
        console.log('training report: %s\nPredictions:', so(report));
        xor.forEach(function(ex){
            prediction = clf.predictSync(ex[0]);
            console.log('   %d XOR %d => %d', ex[0][0], ex[0][1], prediction);
            prediction="prediciendo desde cbba";
            return {
            prediction:1    
            };
        });
    });
exports.prediction =prediction;

But I can not show in app.js . The variable reaches undefined .

Code:

var ror = require('./node_modules/node-svm/examples/evaluation-example');
console.log(ror.prediction);

nodejs

asked by hubman 15.09.2016 в 06:45

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1 answer

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score 1 · Accepted Answer

The value that you export is obtained asynchronously and you are exporting it when the value has not yet been calculated, which is why it reaches you as undefined .

The solution is to export in your module a function that accepts callback and send in it the value when it is calculated.

'use strict';
var so = require('stringify-object');
var svm = require('../lib');

var xor = [
    [[0, 0], 0],
    [[0, 1], 1],
    [[1, 0], 1],
    [[1, 1], 0]
];

function prediction(callback) {
  // initialize predictor
  var clf = new svm.CSVC({
    kFold: 1
  });
  clf.train(xor)
    .progress(function(progress) {
      console.log('training progress: %d%', Math.round(progress * 100));
    })
    .spread(function(model, report) {
      console.log('training report: %s\nPredictions:', so(report));
      xor.forEach(function(ex) {
        // No puedes usar la variable prediction 
        // porque ocultarías el nombre de la función
        var pred = clf.predictSync(ex[0]);
        console.log('   %d XOR %d => %d', ex[0][0], ex[0][1], pred);
        // Esto eliminaría el valor por eso lo comento
        //prediction = "prediciendo desde cbba";

        // Invocas el callback con los datos
        callback(null, pred);
        return {
          prediction: 1
        };
      });
    });
}

// Exportas la función
exports.prediction = prediction;

To use it you should call it this way

var ror = require('./node_modules/node-svm/examples/evaluation-example').prediction;

ror(function(error, prediction) {
    console.log(prediction);
});

This function will be called several times since your prediction value is within a cycle forEach .

If you wonder why I use (error, valor) reads

link

If you do not handle the error, simply delete the parameter.