Grouping elements in array by multiple properties is the closest match to my question as it indeed groups objects by multiple keys in an array. Problem is this solution doesn't sum up the properties value then remove the duplicates, it instead nests all the duplicates in a two-dimensional arrays.
Expected behavior
I have an array of objects which must be grouped by shape
and color
.
var arr = [
{shape: 'square', color: 'red', used: 1, instances: 1},
{shape: 'square', color: 'red', used: 2, instances: 1},
{shape: 'circle', color: 'blue', used: 0, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 4},
{shape: 'circle', color: 'red', used: 1, instances: 1},
{shape: 'circle', color: 'red', used: 1, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 5},
{shape: 'square', color: 'red', used: 2, instances: 1}
];
Objects in this array are considered duplicates only if both their shape
and color
are the same. If they are, I want to respectively sum up their used
and instances
values then delete the duplicates.
So in this example result array may only contain four combinations : square red
, square blue
, circle red
, circle blue
Problem
I tried a simpler approach here:
var arr = [
{shape: 'square', color: 'red', used: 1, instances: 1},
{shape: 'square', color: 'red', used: 2, instances: 1},
{shape: 'circle', color: 'blue', used: 0, instances: 0},
{shape: 'square', color: 'blue', used: 4, instances: 4},
{shape: 'circle', color: 'red', used: 1, instances: 1},
{shape: 'circle', color: 'red', used: 1, instances: 0},
{shape: 'square', color: 'red', used: 4, instances: 4},
{shape: 'square', color: 'red', used: 2, instances: 2}
];
result = [];
arr.forEach(function (a) {
if ( !this[a.color] && !this[a.shape] ) {
this[a.color] = { color: a.color, shape: a.shape, used: 0, instances: 0 };
result.push(this[a.color]);
}
this[a.color].used += a.used;
this[a.color].instances += a.instances;
}, Object.create(null));
console.log(result);
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