Lodash group by multiple properties if property value is true

Question

I have an array of vehicles that need to be grouped by make and model, only if the \'selected\' property is true. The resulting object should contain properties for make mod

Answer 1

You don't need to reiterate all the array object. with loadash, you can make simple as below:

_.mapValues(_.groupBy(object, 'yourKeys'))

Answer 2

You can use Array.prototype.reduce(), and do it in one loop O(n):

var arr = [{"id":1,"selected":true,"makeCode":"Make-A","modelCode":"Model-a","trimCode":"trim-a","yearCode":"2012"},{"id":2,"selected":false,"makeCode":"Make-A","modelCode":"Model-a","trimCode":"trim-a","yearCode":"2013"},{"id":3,"selected":true,"makeCode":"Make-B","modelCode":"Model-c","trimCode":"trim-a","yearCode":"2014"},{"id":25,"selected":true,"makeCode":"Make-C","modelCode":"Model-b","trimCode":"trim-b","yearCode":"2012"},{"id":26,"selected":true,"makeCode":"Make-C","modelCode":"Model-b","trimCode":"trim-a","yearCode":"2013"},{"id":29,"selected":false,"makeCode":"Make-A","modelCode":"Model-g","trimCode":"trim-a","yearCode":"2013"},{"id":2,"selected":true,"makeCode":"Make-A","modelCode":"Model-h","trimCode":"trim-a","yearCode":"2013"}];

var result = arr.reduce(function(map, obj) {
  if(!obj.selected) {
    return map;
  }
  
  var makeCode = map[obj.makeCode] = map[obj.makeCode] || {};
  
  var modelCode = makeCode[obj.modelCode] = makeCode[obj.modelCode] || { count: 0 };
  
  modelCode.count++;
  
  return map;
}, Object.create(null));

console.log(result);

A more readable, and modern version using destructuring:

const arr = [{"id":1,"selected":true,"makeCode":"Make-A","modelCode":"Model-a","trimCode":"trim-a","yearCode":"2012"},{"id":2,"selected":false,"makeCode":"Make-A","modelCode":"Model-a","trimCode":"trim-a","yearCode":"2013"},{"id":3,"selected":true,"makeCode":"Make-B","modelCode":"Model-c","trimCode":"trim-a","yearCode":"2014"},{"id":25,"selected":true,"makeCode":"Make-C","modelCode":"Model-b","trimCode":"trim-b","yearCode":"2012"},{"id":26,"selected":true,"makeCode":"Make-C","modelCode":"Model-b","trimCode":"trim-a","yearCode":"2013"},{"id":29,"selected":false,"makeCode":"Make-A","modelCode":"Model-g","trimCode":"trim-a","yearCode":"2013"},{"id":2,"selected":true,"makeCode":"Make-A","modelCode":"Model-h","trimCode":"trim-a","yearCode":"2013"}];

const result = arr.reduce((acc, { selected, makeCode, modelCode }) => {
  if(!selected) return acc;
  
  if(!acc[makeCode]) acc[makeCode] = {};
  
  const make = acc[makeCode];
  
  if(!make[modelCode]) make[modelCode] = { count: 0 };
  
  make[modelCode].count++;
  
  return acc;
}, Object.create(null));

console.log(result);