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

Answer 1

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
      }]
   };

Answer 2

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);

Answer 3

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'));*/

Answer 4

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>';

Answer 5

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.