From array of Object , get array of only matched key value

Question

Suppose I have an array of object:

var students = [{name: 'Nick',achievements: 158,points: 1473}, {name: 'Nick',achievements: '175',points: '16375'}, 
{name: 'Ramon',achievements: '55',points: '2025'}];

I want to extract points from name Nick only in an array.

Like if (name=='Nick), O/P should be [1473,16375]

I tried:

var arrayPoints = students.map(function (el) { 
    if(el.name=='Nick'){
        return el.points
    }
});

But it gives me o/p:

console.log(arrayPoints)

[1473,16375,undefined] o/p

Nina Scholz · Accepted Answer · 2021-02-16 09:09:02Z

A look to the methods:

Array#map returns a (new) value for each element.
Array#filter returns exactly the element if the return value of the callback is truthy

You could take two steps, one for filtering the items and another to get the values from.

const
    students = [{ name: 'Nick', achievements: 158, points: 1473 }, { name: 'Nick', achievements: '175', points: '16375' }, { name: 'Ramon', achievements: '55', points: '2025' }],
    arrayPoints = students
        .filter(student => student.name === 'Nick') 
        .map(student => student.points);

console.log(arrayPoints);

If Array#flatMap is implemented, you could take a single loop and filter and return a value.

The empty array has no items and this array is a neutral value which does not turn up in the result array.

const
    students = [{ name: 'Nick', achievements: 158, points: 1473 }, { name: 'Nick', achievements: '175', points: '16375' }, { name: 'Ramon', achievements: '55', points: '2025' }],
    arrayPoints = students
        .flatMap(student => student.name === 'Nick'
            ? student.points
            : []
        );

console.log(arrayPoints);

prasanth · Accepted Answer · 2021-02-16 09:06:48Z

2

For single loop result without undefined. You could do with Array#reduce

students.reduce(function (acc,el) { 
    if(el.name=='Nick'){
        acc.push(el.points)
    }
    return acc
},[]);

answered Feb 16, 2021 at 9:06

prasanth

22.6k4 gold badges33 silver badges57 bronze badges

Comments

Ran Turner · Accepted Answer · 2021-02-16 13:25:34Z

2

You can use reduce for that:

The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in single output value.

So You can use it and check if the name is indeed Nick (el is the currentValue).

if so then push the points to the accumulator (which is arr).

[] represent the initialValue passed to the reduce function.

var arrayPoints = students.reduce((arr, el) => 
    (el.name === 'Nick' && arr.push(el.points), arr), [])

You can find more info regarding reduce here:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

edited Feb 16, 2021 at 13:25

answered Feb 16, 2021 at 9:10

Ran Turner

18.7k9 gold badges60 silver badges60 bronze badges

Collectives™ on Stack Overflow

From array of Object , get array of only matched key value

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related