Need to merge objects with the same keys but different values

Question

I want to find the shortest and most beautiful way to convert an array of objects with the same values of the category key:

[{
  "label": "Apple",
  "category": "Fruits"
}, {
  "label": "Orange",
  "category": "Fruits"
}, {
  "label": "Potato",
  "category": "Vegetables"
}, {
  "label": "Tomato",
  "category": "Vegetables"
}, {
  "label": "Cherry",
  "category": "Berries"
}]

to the one with grouped labels from the same category:

[{
  "label": ["Apple", "Orange"],
  "category": "Fruits"
}, {
  "label": ["Potato", "Tomato"],
  "category": "Vegetables"
}, {
  "label": ["Cherry"],
  "category": "Berries"
}]

Nina Scholz · Accepted Answer · 2016-09-09 13:55:27Z

4

You could use an object as hash table and group the categories.

var data = [{ "label": "Apple", "category": "Fruits" }, { "label": "Orange", "category": "Fruits" }, { "label": "Potato", "category": "Vegetables" }, { "label": "Tomato", "category": "Vegetables" }, { "label": "Cherry", "category": "Berries" }],
    grouped = [];

data.forEach(function (a) {
    if (!this[a.category]) {
        this[a.category] = { label: [], category: a.category };
        grouped.push(this[a.category]);
    }
    this[a.category].label.push(a.label);
}, Object.create(null));

console.log(grouped);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Sep 9, 2016 at 13:55

Nina Scholz

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Comments

Adam Boduch · Accepted Answer · 2016-09-09 17:21:51Z

2

Here's how I would do this using lodash:

_(coll)
  .groupBy('category')
  .map((v, k) => ({
    category: k,
    label: _.map(v, 'label')
  }))
  .value()

Basically, groupBy() creates an object with unique categories as keys. Then, map() turns this object back into an array, where each item has the structure you need.

answered Sep 9, 2016 at 17:21

Adam Boduch

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Comments

Subodh Ghulaxe · Accepted Answer · 2016-09-09 14:28:33Z

1

Here is my attempt to solve your problem

var result = [];
var input = [{
  "label": "Apple",
  "category": "Fruits"
}, {
  "label": "Orange",
  "category": "Fruits"
}, {
  "label": "Potato",
  "category": "Vegetables"
}, {
  "label": "Tomato",
  "category": "Vegetables"
}, {
  "label": "Cherry",
  "category": "Berries"
}];
var cat = [];
for(i = 0; i < input.length; i++) {
  if(!cat[input[i].category]) {
    cat[input[i].category] = {category: input[i].category, label:[input[i].label]};
    result.push(cat[input[i].category]);
  } else {
    cat[input[i].category].label.push(input[i].label);
  }
}
console.log(result);

answered Sep 9, 2016 at 14:28

Subodh Ghulaxe

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