Find closest to the number inside array

Question

I have below array

const floorPerDayMilestones = [25, 50, 75, 100, 125, 150, 175, 200]

From the frontEnd user enters any number say it is

const number = 136

I need to find closest to the number but the lesser one. So the output should be 125

Even if the number is 149 the output should be 125

How can I do this. I tried many way but could get the answer.

Thanks!!!

Your problem statement is unclear. What should be returned for a value such as 12, 125, or 300? — 31piy, Dec 03 '18 at 13:17
Walk through the array until you find a bigger number, then take the one before that. — Andreas, Dec 03 '18 at 13:17
You could do `Math.floor(x / 25) * 25;` To get the nearest multiple of 25 (rounded down) to your number. — Jack hardcastle, Dec 03 '18 at 13:18

score 1 · Answer 1 · answered Dec 03 '18 at 13:18

You can use Array.reduce for this

const floorPerDayMilestones = [25, 50, 75, 100, 125, 150, 175, 200]

function getClosestNumber(d) {
  return floorPerDayMilestones.reduce((a, b) => b <=d && a < b ? b : a, 0 )
}

console.log(getClosestNumber(135) || 'No lesser number available')

console.log(getClosestNumber(149) || 'No lesser number available')

console.log(getClosestNumber(22) || 'No lesser number available')

score 1 · Answer 2 · answered Dec 03 '18 at 13:18

1

Maybe you should look at this: get closest number out of array

And in your foreach, save your closest number in a var. Then check if your number is bigger than the one in your array . if yes, take your last var, else continue your foreach

answered Dec 03 '18 at 13:18

Arnaud Toupet

11
1

Nurbol Alpysbayev · Answer 3 · 2018-12-03T13:37:59.617

1

Try this

const floorPerDayMilestones = [25, 50, 75, 100, 125, 150, 175, 200];
    
const number = 136;
    
    
const nextLesser = floorPerDayMilestones.reduce((nl, curr) => (curr <= number) && (curr > nl) ? curr : nl , 0)

console.log(nextLesser)

Used Array.prototype.reduce

edited Dec 03 '18 at 13:37

answered Dec 03 '18 at 13:19

Nurbol Alpysbayev

19,522
3
54
89

Its give me `100` when i put `number` `125`. I need `125` – Profer Dec 03 '18 at 13:37
@Profer try again, I changed the code a bit. All that was needed to do is change `<` to `<=` – Nurbol Alpysbayev Dec 03 '18 at 13:39
You are welcome! Consider selecting the best answer as well. – Nurbol Alpysbayev Dec 03 '18 at 13:56

score 1 · Answer 4 · answered Dec 03 '18 at 13:20

You can sort the array in ascending order and then find the index of number that is immediately higher than number then one position less of that value will be the immediate number that is less than number

const floorPerDayMilestones = [25, 50, 75, 100, 125, 150, 175, 200]
const number = 136;
floorPerDayMilestones.sort((a,b)=> a-b);
var index = floorPerDayMilestones.findIndex(val => val>number);
var num = floorPerDayMilestones[index-1];
console.log(num);

barbsan · Answer 5 · 2018-12-03T14:07:42.910

1

You can also filter out numbers greater than given and select max from this subset.

const floorPerDayMilestones = [25, 50, 75, 100, 125, 150, 175, 200]

const number = 136

const filtered = floorPerDayMilestones.filter(el=>el<=number);

console.log(Math.max(...filtered))

Or, if you're already using lodash (only in this case - don't import lodash just to use solution below), you can do it with maxBy. maxBy treats numbers greater than number as null.

const floorPerDayMilestones = [25, 50, 75, 100, 125, 150, 175, 200]

const number = 136

let result = _.maxBy(floorPerDayMilestones, el=>el<=number?el:null);

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

edited Dec 03 '18 at 14:07

answered Dec 03 '18 at 13:27

barbsan

3,418
11
21
28

Cool! But I believe this is two set of operations vs one when using reduce. – Nurbol Alpysbayev Dec 03 '18 at 13:32
1

@NurbolAlpysbayev Right, it's rather more readable than efficient, but there were already 2 answers with `reduce` – barbsan Dec 03 '18 at 13:35
Its give me `100` when i put `number` `125`. I need `125` – Profer Dec 03 '18 at 13:37
@Profer I understood "*closest to the number but the lesser one*" as `<`, but if you need lesser or equal then it's enough to replace `<` to `<=`. I've updated my code – barbsan Dec 03 '18 at 13:48
@barbsan Oh no, why suggesting lodash for such a simple task. Lodash should actually be deprecated nowadays, native features are good. – Nurbol Alpysbayev Dec 03 '18 at 13:58
@NurbolAlpysbayev because OP has tag lodash, so propably already uses it – barbsan Dec 03 '18 at 13:59
@barbsan Oh ok, fair. – Nurbol Alpysbayev Dec 03 '18 at 14:01

Akrion · Answer 6 · 2018-12-03T19:26:44.693

With lodash you could use _.sortedIndex:

const numbers = [25, 50, 75, 100, 125, 150, 175, 200]

const closestNum = (arr, n) => {
  let index = _.sortedIndex(arr, n)
  return arr[index] == n ? arr[index] : arr[index-1]
}

console.log(closestNum(numbers, 135))  // 120
console.log(closestNum(numbers, 160))  // 150
console.log(closestNum(numbers, 180))  // 175

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

With JS you can simply use Array.reduceRight:

const numbers = [25, 50, 75, 100, 125, 150, 175, 200]

const closestNum = (arr, n) => arr.reduceRight((r,c) => !r && c < n ? c : r, 0)

console.log(closestNum(numbers, 135))  // 120
console.log(closestNum(numbers, 160))  // 150
console.log(closestNum(numbers, 180))  // 175

Since it will start from the right side all you care about is to find the first number less than your argument n.

You could also do Array.reverse and then just Array.filter (use Array.from if you do not want to mutate the array):

const numbers = [25, 50, 75, 100, 125, 150, 175, 200]

const closestNum = (arr, n) => arr.reverse().find(x => x < n)

// To not mutate use `Array.from`
// const closestNum = (arr, n) => Array.from(arr).reverse().find(x => x < n)

console.log(closestNum(numbers, 135))  // 120
console.log(closestNum(numbers, 160))  // 150
console.log(closestNum(numbers, 180))  // 175

lloydaf · Accepted Answer · 2018-12-03T13:22:44.593

0

If it's sorted in ascending order like in the question this should work.

const floorPerDayMilestones = [25, 50, 75, 100, 125, 150, 175, 200];
const number = 136;

function findClosest(arr, num) {
  for (let i = 0; i < arr.length; ++i) {
    if (arr[i] > num) {
      return arr[i - 1];
    }
  }
}

console.log(findClosest(floorPerDayMilestones,number));

edited Dec 03 '18 at 13:22

answered Dec 03 '18 at 13:17

lloydaf

605
3
17

@Andreas was a typo, I was returning the index not the element, I think it works now – lloydaf Dec 03 '18 at 13:23
@Profer if you find an answer suitable you can mark it as accepted and the question can be closed. :-) – lloydaf Dec 03 '18 at 16:22

Find closest to the number inside array

7 Answers7