Return array of unique objects from another array of objects with multiple constraints

Question

I have an array of objects like this:

[{"name" : "Annie", "number" : 25},
{"name" : "Zeus", "number" : 25},
{"name" : "John", "number" : 40},
{"name" : "John", "number" : 32},
{"name" : "Zeus", "number" : 75},
{"name" : "Zeus", "number" : 32} ]

I would like to filter this such that I have one instance of each unique name and that instance must give me the largest number less than or equal to 40. The above case, if filtered, would return:

[{"name" : "Annie", "number" : 25},
{"name" : "John", "number" : 40},
{"name" : "Zeus", "number" : 32} ]

The final array does not have to be sorted in any particular order.

Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it in the question itself. Questions without a clear problem statement are not useful to other readers. See: How to create a Minimal, Complete, and Verifiable example. — user177800
– user177800, Commented May 9, 2016 at 1:25
You should probably loop over the array with filter and create an index object of the names encountered. Keep the first of each with a value <= 40 and if duplicates are found, keep the one with the highest value <= 40. What have you tried? — RobG
– RobG, Commented May 9, 2016 at 1:26

BryanGrezeszak · Accepted Answer · 2016-05-09 01:59:46Z

0

It's a pretty simple challenge with an O(N) solution. A function do so so would be this:

function solution(A)
{
    var endObj = {};
    for (var i=0, ii=A.length; i<ii; i++)
    {
        var val = A[i];

        if (val.number > 40)
            continue;

        if (!endObj[val.name]) {
            endObj[val.name] = val;
            continue;
        }

        if (endObj[val.name].number < val.number)
            endObj[val.name] = val;
    }

    var endArr = [];
    for (var key in endObj)
        endArr.push(endObj[key]);

    return endArr;
}

I just tracked the names by using them as the key to a new object, then convert that object to a keyless Array once finished.

JSfiddle example here: https://jsfiddle.net/qa7vzvp5/

answered May 9, 2016 at 1:59

BryanGrezeszak

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1 Comment

docwelch Over a year ago

Thanks, this really helps and works great for my case.

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