lodash - Count duplicate and then remove them

Question

I am trying to use lodash to first count how many duplicates are in an array of objects and the remove the duplicate (keeping the counter).

The code I have so far se

Answer 1

You're looking for a reduce function, which is widely available in native JS. Here's a full code sample that does the job without Lodash:

    const inputArray = [
        {id: 1, name: "test"},
        {id: 2, name: "test 2"},
        {id: 3, name: "test 3"},
        {id: 4, name: "test 4"},
        {id: 1, name: "test "},
        {id: 2, name: "test 2"}
    ];

    const uniqueArrayWithCounts = inputArray.reduce((accum, val) => {
        const dupeIndex = accum.findIndex(arrayItem => arrayItem.id === val.id);

        if (dupeIndex === -1) {
          // Not found, so initialize.
          accum.push({
            qty: 1,
            ...val
          });
        } else {
          // Found, so increment counter.
          accum[dupeIndex].qty++;
        }
        return accum;
    }, []);

    console.log(uniqueArrayWithCounts);

Here's a good way to think about this:

1) Do you want the output array to be the same size (e.g. 1:1, every input has an output)? Then you're going to want to use map.

2) Do you want the output array to be a different size (usually smaller)? Then you're going to want to use reduce (or filter, etc).

Because we want to remove duplicates, that should lead you to use #2. That'll at least get you started going down the right path next time!