How to get the index of the 5 smallest values in an array?

Question

I am trying to get the indexes of the 5 smallest values in an array.

I've tried the code below, however it gives the error: Math.min.apply(...).indexOf is not a function. I'm just not sure what I can use as an alternative?

var smallest = [];
for (var i = 0, length = distances.length; i < length; i++) {
    var min = Math.min.apply(null,distances).indexOf();
    if (smallest.length <= 5) {
        smallest.push(min);
    }
    console.log(smallest);
}

Thanks!

Well that expression does not make sense; Math.min() returns a single numeric value. — Pointy
– Pointy, Commented Jul 10, 2019 at 12:18
Object.entries(distances).sort(([i,a],[j,b]) => a - b).map(([index]) => index).slice(0, 5) — Thomas
– Thomas, Commented Jul 10, 2019 at 12:22
What if the same (small) value is in the array twice? Which index do you want? — T.J. Crowder
– T.J. Crowder, Commented Jul 10, 2019 at 12:22

Nina Scholz · Accepted Answer · 2019-07-10 12:24:42Z

5

You could get the keys, sort them with the values and take the top five.

var indices = [...distances.keys()]
        .sort((a, b) => distances[a] - distances[b])
        .slice(0, 5);

answered Jul 10, 2019 at 12:24

Nina Scholz

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2 Comments

Nina Scholz Over a year ago

keys returns an iterator.

Kobe Over a year ago

@charlietfl take a look at mdn

Thomas · Accepted Answer · 2019-07-10 12:34:40Z

3

You can use Object.entries() to get [index, value] pairs that you can now sort by value to get the order.

const distances = [1, 4, 8, 3, 3, 5, 9, 0, 4, 2];
const indices = Object.entries(distances)
                      .sort(([,a],[,b]) => a - b)
                      .map(([index]) => +index)
                      .slice(0, 5)
console.log(indices);

Nina's version is better :)

edited Jul 10, 2019 at 12:34

answered Jul 10, 2019 at 12:25

Thomas

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3 Comments

Kobe Over a year ago

There's no need to declare i or j here, you can just write [,a] and [,b] :)

Thomas Over a year ago

@Kobe thx, wasn't sure. And didn't want to use _ and __ for these unused arguments

Kobe Over a year ago

Yeah, destructuring can get weird sometimes :P

Kobe · Accepted Answer · 2019-07-10 12:41:15Z

0

You could add an index to each element, sort the data in ascending order, then splice the first 5 values:

const data = [1, 4, 8, 3, 3, 5, 9, 0, 4, 2]

const indices = data.map((e,i) => [e, i])
  .sort()
  .splice(0,5)
  .map(([,el]) => el)

console.log(indices)

edited Jul 10, 2019 at 12:41

answered Jul 10, 2019 at 12:21

Kobe

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4 Comments

charlietfl Over a year ago

How would this return the indexes?

Kobe Over a year ago

Ah, yes, ill fix that now @charlietfl

Kobe Over a year ago

@T.J.Crowder haha yes, I always fall victim to not writing in strict mode when writing answers here too.

Thomas Over a year ago

data.slice().map(...) is pointless. map already creates a new Array, you don't need slice() anymore. :)

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