Counting elements in JSON using JavaScript

Question

I hope someone can point me in the right direction, I've burnt hours trying to solve what I think is a simple problem - I've hunted SO and tried various things that were close but no cigar.

I want to count two things from the sample JSON block below.

First I want to count the number of productLine entries, and second I want to count the number of types - by productLine and in total across all productLine(s).

So I'd like to end up with 3 variables with a number assigned to them to represent these three values.

Is anyone able to help?

var products = {
  "product": "Product Name",
  "productLines": [{
    "productLine": "Line 1",
    "types": ["Type 1", "Type 2", "Type 3", "Type 4"]
  }, {
    "productLine": "Line 2",
    "types": ["Type 5", "Type 6", "Type 7", "Type 8"]
  }, {
    "productLine": "Line 3",
    "types": ["Type 9", "Type 10", "Type 11"]
  }, {
    "productLine": "Line 4",
    "types": ["Type 12", "Type 13"]
  }]
};

Output would be something like:

var productLineCount = 4
var productLine[0].name = "Line 1"
var productLine[0].types.count() = 4
var typesCount = 13

whats the expected output u want for this data? the likely format. — Ayan
– Ayan, Commented Jul 23, 2016 at 14:57
like what? cant get u.. @nick. You update the question itself. — Ayan
– Ayan, Commented Jul 23, 2016 at 14:58
What if the same type occurs again in another line, does it increase the count or not? — trincot
– trincot, Commented Jul 23, 2016 at 15:13
The output you provide is JavaScript. You really want to produce code? What do you need this output for? Can you explain the context? You said you wanted a number assigned to them. Where is that in the expected output you provided? — trincot
– trincot, Commented Jul 23, 2016 at 15:17

Rajaprabhu Aravindasamy · Accepted Answer · 2016-07-23 15:07:49Z

1

You can do it by,

var prodLines = products.productLines.length;
var prodLinesTypes = products.productLines.reduce(function(a,b){ 
       return a + (b.types.length) 
}, 0);

console.log(prodLines); //4
console.log(prodLinesTypes); //13

The first one is an obvious one, that is reading the length of an array. But the second one can be done by using .reduce(). It can be done in many ways. But I would suggest you to go with reduce at this context.

edited Jul 23, 2016 at 15:07

answered Jul 23, 2016 at 15:00

Rajaprabhu Aravindasamy

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3 Comments

Nick Myers Over a year ago

Thank you @Rajaprabhu Aravindasamy - I tried this (will have to work my way through the second one and understand it) but the first line gave me a 'Uncaught TypeError: Cannot read property 'length' of undefined' - any idea?

Rajaprabhu Aravindasamy Over a year ago

@NickMyers That is because of your inconsistent property name, look at the last object in the array, It has a property called type whereas others has types.

JasTonAChair Over a year ago

Maybe it's one of these 'Oh dang someone answered before I could post my answer so I'll downvote them' downvotes. We can only assume.

Nenad Vracar · Accepted Answer · 2016-07-23 15:08:23Z

You can use forEach loop and return results in one object

var products = {
  "product": "Product Name",
  "productLines": [{
    "productLine": "Line 1",
    "types": ["Type 1", "Type 2", "Type 3", "Type 4"]
  }, {
    "productLine": "Line 2",
    "types": ["Type 5", "Type 6", "Type 7", "Type 8"]
  }, {
    "productLine": "Line 3",
    "types": ["Type 9", "Type 10", "Type 11"]
  }, {
    "productLine": "Line 4",
    "types": ["Type 12", "Type 13"]
  }]
};

var result = {}
products.productLines.forEach(function(e) {
  result.totalLines = (result.totalLines || 0) + 1;
  e.types.forEach(function(a) {
    result.totalTypes = (result.totalTypes || 0) + 1;
    result[e.productLine + 'Types'] = (result[e.productLine + 'Types'] || 0) + 1;
  });
});

document.body.innerHTML = '<pre>' + JSON.stringify(result, 0, 4) + '</pre>';

Ayan · Accepted Answer · 2016-07-23 15:11:38Z

You can use an custom api like

getter(index, type)

index is the product index, type can be either typeCount or name.

var products = {
  "product": "Product Name",
  "productLines": [{
    "productLine": "Line 1",
    "types": ["Type 1", "Type 2", "Type 3", "Type 4"]
  }, {
    "productLine": "Line 2",
    "types": ["Type 5", "Type 6", "Type 7", "Type 8"]
  }, {
    "productLine": "Line 3",
    "types": ["Type 9", "Type 10", "Type 11"]
  }, {
    "productLine": "Line 4",
    "types": ["Type 12", "Type 13"]
  }]
};

var count = 0;
for (var i = 0, len =  products.productLines.length; i < len; i += 1) {
  count += products.productLines[i].types.length;
}
console.log('productLineCount: ',len);
console.log('typesCount: ', count);

function getter(index, type) {
  var res,
      arr = products.productLines[index];
  if (type === 'name') {
      res = arr.productLine;
  }
  else if (type === 'typeCount') {
    res = arr.types.length;
  }
  return res;
}


console.log('productLine[0].name: ', getter(0, 'name'));
console.log('productLine[0].types.count(): ', getter(0, 'typeCount'));
/*console.log('productLine[1].name: ', getter(1, 'name'));
console.log('productLine[1].types.count(): ', getter(1, 'typeCount'));
console.log('productLine[2].name: ', getter(2, 'name'));
console.log('productLine[2].types.count(): ', getter(2, 'typeCount'));*/

hey @nick does this work? Please validate if we need some other improvements here.

trincot · Accepted Answer · 2016-07-23 15:22:26Z

0

You could get the three counts as follows:

var productLineCount = products.productLines.length;
var productTypesCount = products.productLines.map(line => line.types.length);
var totalTypesCount = productTypesCount.reduce((sum, cur) => sum + cur, 0);

var products = {
  "product": "Product Name",
  "productLines": [{
    "productLine": "Line 1",
    "types": ["Type 1", "Type 2", "Type 3", "Type 4"]
  }, {
    "productLine": "Line 2",
    "types": ["Type 5", "Type 6", "Type 7", "Type 8"]
  }, {
    "productLine": "Line 3",
    "types": ["Type 9", "Type 10", "Type 11"]
  }, {
    "productLine": "Line 4",
    "types": ["Type 12", "Type 13"]
  }]
};

var productLineCount = products.productLines.length;
var productTypesCount = products.productLines.map(line => line.types.length);
var totalTypesCount = productTypesCount.reduce((sum, cur) => sum + cur, 0);

console.log('productLineCount', productLineCount);
console.log('productTypesCount', productTypesCount);
console.log('totalTypesCount', totalTypesCount);

answered Jul 23, 2016 at 15:22

trincot

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1 Comment

Nick Myers Over a year ago

thanks for this - really useful to see this approach

Joabe da Luz · Accepted Answer · 2016-07-23 15:23:59Z

For counting the ProductLines you can do it

number_of_productLines = products.productLines.length

And for counting the types by productLines you can do:

productlines_types_count = [] # List of {'productline': name, 'length': int}
products.productLines.forEach(function(productline){ 
    productlines_types_count.push({'productline': productline.productLine, 'length': productline.types.length})
});

Also fix your json, the last of objects has a 'type' id insteade of 'types':

var products = 
  {
    "product" : "Product Name",
    "productLines": [
      {
        "productLine" : "Line 1",
        "types": ["Type 1", "Type 2", "Type 3", "Type 4"]
      },
      {
        "productLine": "Line 2",
        "types": ["Type 5", "Type 6", "Type 7", "Type 8"]
      },
      {
        "productLine": "Line 3",
        "types": ["Type 9", "Type 10", "Type 11"]
      },
      {
        "productLine": "Line 4",
        "types": ["Type 12", "Type 13"] #here
      }]
   };

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