How group and count elements by lodash

Question

has data

items = {
                0: {id:1,name:'foo'},
                1: {id:2,name:'bar'},
                2: {id:1,name:'foo'}
            };

I wont get counted elements like this

result = {
                0: {id:1,name:'foo', count:2},
                1: {id:2,name:'bar', count:1}
            };

lodash has function _.countBy(items, 'name') it's got {'foo': 2, 'bar':1}, i need id too.

Answer 1

If pure JS approach is acceptable, you can try something like this:

Logiic:

• Loop over array and copy the object and add a property count and set it to 0.
• Now on every iteration update this count variable.
• Using above 2 steps, create a hashMap.
• Now loop over hashMap again and convert it back to array.

var items = [{
    id: 1,
    name: 'foo'
  }, {
    id: 2,
    name: 'bar'
  }, {
    id: 1,
    name: 'foo'
  }
];

var temp = items.reduce(function(p,c){
  var defaultValue = {
    name: c.name,
    id: c.id,
    count: 0
  };
  p[c.name] = p[c.name] || defaultValue
  p[c.name].count++;
  
  return p;
}, {});

var result = [];
for( var k in temp ){
  result.push(temp[k]);
}

console.log(result)