Underscore, Nested Group By and Generate a JSON

Question

I have an array of objects with duplicates and I'm trying to get a unique listing, where uniqueness is defined by a subset of the properties of the object. For example,

Current JSON Object:

[{"x":6811,"y":15551,"a":"a"},
{"x":6811,"y":15551,"a":"b"},
{"x":6811,"y":15551,"a":"c"},
{"x":6811,"y":15552,"a":"c"},
{"x":6812,"y":15551,"a":"c"}]

How to group by two property

The last result is

[{"x":6811,"y":15551,"a":["a","b","c"]},
{"x":6811,"y":15552,"a":["c"]},
{"x":6812,"y":15551,"a":["c"]}]

How to use underscore to make it unique and generate a merge "a" Key

Answer 1

You can use groupBy to create a composite key on x and y. Then, use map to iterate through the grouped data.

var data = [{"x":6811,"y":15551,"a":"a"},{"x":6811,"y":15551,"a":"b"},{"x":6811,"y":15551,"a":"c"},{"x":6811,"y":15552,"a":"c"},{"x":6812,"y":15551,"a":"c"}]
var groups = _.groupBy(data, ({x,y}) => `${x}_${y}`);
var result = _.map(groups, o => ({...o[0], a : _.pluck(o,'a')}));
console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>