Building array of objects from parsed csv files in node

Question

I have multiple csv files of the form

• model1A
• model1B
• model2A
• model2B

where each csv is an array i.e. model1A = [1, 1, 1]

I want to parse these csvs and create a single array containing all these models, where each element in the array is an object corresponding to one particular model, i.e.

finalArray = [ 
  { 
    "model" :   "model1",
    "A"     :   [1, 1, 1],
    "B"     :   [2, 2, 2]
  },
  { 
    "model" :   "model2",
    "A"     :   [3, 3, 3],
    "B"     :   [4, 4, 4]
  }
]

The code I have so far is

var csv = require('csv');
var fs = require('fs');
var parser = csv.parse();
var util = require('util');
var junk = require('junk');
var _ = require('lodash');
var models = [];


fs.readdir(__dirname+'/data', function(err, files) {
    var model = {};
    _.forEach(files, function(n, key) {

        console.log('Analysing file: ' + n);
        var modelName;
        var modelNum;
        var modelParam;


        modelNum = n.match(/\d+/)[0];
        modelName = 'model' + modelNum;
        modelParam = (n.substring(0, n.indexOf('.'))).replace(modelName,'');

        model.model = modelName;
        model[modelParam] = [];
        models.push(model);

        //if (Object.keys(model).length === 3) {
        //    models.push(model);
        //    model = {};
        //}


        fs.createReadStream(__dirname+'/data/'+n).pipe(csv.parse()).pipe(csv.transform(function(row) {
            model[modelParam].push(row);

        })).on('readable', function(){
            while(this.read()){}
        }).on('end', function() {
            console.log('finished reading file ' + n);
            if (key === (files.length - 1)) {
                fs.writeFile('result.json', JSON.stringify(models), function (err) {
                    if (err) throw err;
                    console.log(models.length + ' model(s) parsed');
                    console.log('done');
                });
            }

        }).on('error', function(error) {
            console.log(error);
        });    
    });
});

I know one of my issues is I am pushing the model to the array to soon, resulting in a final array of the form below, where model1 is being overwritten by model2

[ { model: 'model2', A: [], B: [] },
  { model: 'model2', A: [], B: [] },
  { model: 'model2', A: [], B: [] },
  { model: 'model2', A: [], B: [] } ]

That's why I tried this code

if (Object.keys(model).length === 3) {
  models.push(model);
  model = {};
}

but of course this couldn't work because the fs.createReadStream is async and I am clearing the model with model = {} before it can run properly.

I'm at the stage now where I feel I'm going around in circles and just making things worse. I wanted to create something more generic, however, now I would be delighted to get it working for the case presented here and then I can look at improving it.

Any help would be really appreciated!

---

Update 1

Following saquib khan's suggestion of moving the var model = {} inside the loop has helped get me closer to my goal, but it's still not right. Below is the current result

[
    {
        "model": "model1",
        "A": [
            [
                "1"
            ],
            [
                "2"
            ],
            [
                "3"
            ],
            [
                "4"
            ]
        ]
    },
    {
        "model": "model1",
        "B": [
            [
                "1"
            ],
            [
                "2"
            ],
            [
                "3"
            ],
            [
                "4"
            ]
        ]
    },
    {
        "model": "model2",
        "A": [
            [
                "1"
            ],
            [
                "2"
            ],
            [
                "3"
            ],
            [
                "4"
            ]
        ]
    },
    {
        "model": "model2",
        "B": [
            [
                "1"
            ],
            [
                "2"
            ],
            [
                "3"
            ],
            [
                "4"
            ]
        ]
    }
]

---

Update 2

Also following Denys Denysiuk's suggestion, the result is closer to what I want, but still just short

[
    {
        "model": "model1",
        "A": [
            "1",
            "2",
            "3",
            "4"
        ]
    },
    {
        "model": "model1",
        "B": [
            "1",
            "2",
            "3",
            "4"
        ]
    },
    {
        "model": "model2",
        "A": [
            "1",
            "2",
            "3",
            "4"
        ]
    },
    {
        "model": "model2",
        "B": [
            "1",
            "2",
            "3",
            "4"
        ]
    }
]

This would work, if I could just somehow iterate over that final array of objects, merging objects with a matching model name. I'm currently looking through the lodash docs to see if I can figure something out. I will post back here if I do.

Answer 1

There is a very small coding error in your code.

var model = {}; should be inside forEach loop.

Try below code:

var csv = require('csv');
var fs = require('fs');
var parser = csv.parse();
var util = require('util');
var junk = require('junk');
var _ = require('lodash');
var models = [];


fs.readdir(__dirname+'/data', function(err, files) {

    _.forEach(files, function(n, key) {

        console.log('Analysing file: ' + n);
        var model = {};
        var modelName;
        var modelNum;
        var modelParam;


        modelNum = n.match(/\d+/)[0];
        modelName = 'model' + modelNum;
        modelParam = (n.substring(0, n.indexOf('.'))).replace(modelName,'');

        model.model = modelName;
        model[modelParam] = [];
        models.push(model);

        //if (Object.keys(model).length === 3) {
        //    models.push(model);
        //    model = {};
        //}


        fs.createReadStream(__dirname+'/data/'+n).pipe(csv.parse()).pipe(csv.transform(function(row) {
            model[modelParam].push(row);

        })).on('readable', function(){
            while(this.read()){}
        }).on('end', function() {
            console.log('finished reading file ' + n);
            if (key === (files.length - 1)) {
                fs.writeFile('result.json', JSON.stringify(models), function (err) {
                    if (err) throw err;
                    console.log(models.length + ' model(s) parsed');
                    console.log('done');
                });
            }

        }).on('error', function(error) {
            console.log(error);
        });    
    });
});

Answer 2

Try this out:

fs.readdir(__dirname+'/data', function(err, files) {

    _.forEach(files, function(n, key) {

        console.log('Analysing file: ' + n);            

        var modelNum = n.match(/\d+/)[0];
        var modelName = 'model' + modelNum;
        var modelParam = (n.substring(0, n.indexOf('.'))).replace(modelName,'');

        var model = {};
        var isNewModel = true;
        for(var i = 0; i < models.length; i++) {
            if(models[i].model == modelName) {
               model = models[i];
               isNewModel = false;
               break;
            }
        }
        if(isNewModel) {
            model.model = modelName;
            models.push(model);
        }

        model[modelParam] = [];

        fs.createReadStream(__dirname+'/data/'+n).pipe(csv.parse()).pipe(csv.transform(function(row) {
            model[modelParam].push(row[0]);

        })).on('readable', function(){
            while(this.read()){}
        }).on('end', function() {
            console.log('finished reading file ' + n);
            if (key === (files.length - 1)) {
                fs.writeFile('result.json', JSON.stringify(models), function (err) {
                    if (err) throw err;
                    console.log(models.length + ' model(s) parsed');
                    console.log('done');
                });
            }

        }).on('error', function(error) {
            console.log(error);
        });    
    });