How can I remove an object from array of objects based on max value in javascript

I've got an array of objects that looks like this:

[ { person: 'Fred', scoreTotal: 29 },
{ person: 'Alice', scoreTotal: 34 },
{ person: 'Alice', scoreTotal: 22 },
{ person: 'Mary', scoreTotal: 14 },
{ person: 'Bob', scoreTotal: 33 },
{ person: 'Bob', scoreTotal: 13 },
{ person: 'Bob', scoreTotal: 22 },
{ person: 'Joe', scoreTotal: 28 }]


and where there are multiple objects for a given person -> I want to keep the top "X". For example:

a. top 1 result for a person
Result would look like this:

[ { person: 'Fred', scoreTotal: 29 },
{ person: 'Alice', scoreTotal: 34 },
{ person: 'Mary', scoreTotal: 14 },
{ person: 'Bob', scoreTotal: 33 },
{ person: 'Joe', scoreTotal: 28 }]


b. top 2 results for a person
Result would look like this:

[ { person: 'Fred', scoreTotal: 29 },
{ person: 'Alice', scoreTotal: 34 },
{ person: 'Alice', scoreTotal: 22 },
{ person: 'Mary', scoreTotal: 14 },
{ person: 'Bob', scoreTotal: 33 },
{ person: 'Bob', scoreTotal: 22 },
{ person: 'Joe', scoreTotal: 28 }]


Is there a way to achieve this using something like Lodash?

I think I'm heading in the right direction with this but not quite there yet:

for (var i = 0; i < t.length - 1; i++) {
if (
t[i].golfer === t[i + 1].golfer &&
t[i].scoreTotal < t[i + 1].scoreTotal
) {
delete t[i];
}


}

// remove the "undefined entries"

t = t.filter(function(el) {
return typeof el !== "undefined";
});
console.log(t);


3 Answers
3

Here is a solution with lodash...

function pickTopX(data, x) {
let grouped = _.groupBy(data, 'person');
let sorted = _.sortBy(grouped, 'scoreTotal');
let sliced = _.map(sorted, function(pair) {
return _.take(pair, x)
});
let result = _.flatten(sliced);
return result;
}


This isn't a full answer, just a tip. Don't use delete array[index], use array.splice. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice for more info.

delete array[index]

array.splice

The next suggestion is to clarify whether you actually need to modify the array, or just get a new array without some of the original array's data. If you do not need to modify the original, it is far better to just use a function like reduce, or use a for loop to selectively copy items into the new array.

Using only ES6, you can use 2 reduces. First is to group the arrays. the second is to get the number of top per group.

reduce

let arr = [{"person":"Fred","scoreTotal":29},{"person":"Alice","scoreTotal":34},{"person":"Alice","scoreTotal":22},{"person":"Mary","scoreTotal":14},{"person":"Bob","scoreTotal":33},{"person":"Bob","scoreTotal":13},{"person":"Bob","scoreTotal":22},{"person":"Joe","scoreTotal":28}];

let getTop = (a, t) => {
return Object.values(a.reduce((c, v) => {
c[v.person] = c[v.person] || ;
c[v.person].push(v);
return c;
}, {})).reduce((c, v) => {
v.sort((a, b) => b.scoreTotal - a.scoreTotal);
c = c.concat(v.slice(0, t));
return c;
}, );
}


let result1 = getTop(arr, 1);
let result2 = getTop(arr, 2);

console.log(result1);
console.log(result2);

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