javascript - merge array object together - lodash

Question

So I have an array of items like this:

items = [
    {
        amount: 2,
        name: 'bike'
    },
    {
        amount: 1,
        name: 'boat'
    },
    {
        amount: 3,
        name: 'bike'
    }
]

Now, I would like to merge this array so that there would be no duplicates of bike and still know how many bikes there are in total.

so my result array would look like this:

items = [
    {
        amount: 5,
        name: 'bike'
    },
    {
        amount: 1,
        name: 'boat'
    }
]

In order to keep my code short I have been advised using lodash and I've been looking at the different ways to merge arrays together. But to be honest it quite confusing to figure out what the best approach would be, which is why I'm asking you guys ^^

Answer 1

You can use .groupBy with .map, and _.sum for calculate amount, like so

var items = [{
    amount: 2,
    name: 'bike'
}, {
    amount: 1,
    name: 'boat'
}, {
    amount: 3,
    name: 'bike'
}];

var res = _(items)
    .groupBy('name')
    .map(function (el, name) {
        return {
            name: name,
            amount: _.sum(el, 'amount')
        };
    })    
    .value();

console.log(res);

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