Javascript find closest number in array without going under

Question

I have an array of numbers, for example [300, 500, 700, 1000, 2000, 3000] and I want to find the closest number, without going under the number given.

For instance, searching for 2200 would return 3000 (NOT 2000).

However, if I search for 3200 as there is nothing higher in the array, it should return 3000 as there are no other choices.

I can get the closest number that is under the value using:

if (sizeToUse == null || Math.abs(this - monitorWidth) < Math.abs(sizeToUse - monitorWidth)) {
                sizeToUse = this;
            }

However, I can't get the whole thing to work. My full code is:

$(function() {

var monitorWidth = window.screen.availWidth,
    sizeToUse = null,
    upscaleImages = false;

$('.responsive-img').each(function(){

    var sizeData = $(this).attr('data-available-sizes');
    sizeData = sizeData.replace(' ', '');

    var sizesAvailable = sizeData.split(',');
    sizesAvailable.sort(function(a, b){return b-a});

    $.each(sizesAvailable, function(){
        if(upscaleImages){
            if (sizeToUse == null || Math.abs(this - monitorWidth) < Math.abs(sizeToUse - monitorWidth)) {
                sizeToUse = this;
            }
        }
        else{
            //We don't want to upscale images so we need to find the next highest image available
        }

    });

    console.log('Size to use ' + sizeToUse + ' monitor width ' + monitorWidth);

});


});

Could you remove the 3/4th of the code that has nothing to do with the question? — James Curran, Jul 31 '14 at 14:33
I've sorted the array using: sizesAvailable.sort(function(a, b){return b-a}); — Amo, Jul 31 '14 at 14:35
Possible duplicate of [get closest number out of array](http://stackoverflow.com/questions/8584902/get-closest-number-out-of-array) — Dan Mindru, Oct 04 '16 at 12:28

score 6 · Accepted Answer · answered Jul 31 '14 at 14:40

You can use this code :

function closest(arr, closestTo){

    var closest = Math.max.apply(null, arr); //Get the highest number in arr in case it match nothing.

    for(var i = 0; i < arr.length; i++){ //Loop the array
        if(arr[i] >= closestTo && arr[i] < closest) closest = arr[i]; //Check if it's higher than your number, but lower than your closest value
    }

    return closest; // return the value
}

var x = closest(yourArr, 2200);

Fiddle : http://jsfiddle.net/ngZ32/

This appears to do exactly what I need with the minimal amount of code. Excellent answer. Thanks — Amo, Jul 31 '14 at 14:56

score 3 · Answer 2 · answered Mar 27 '21 at 19:22

3

Another approach is to find the first candidate greater than or equal to the one you want, and take the result, returning the last element if there are no matches:

  function closestNumberOver(x, arr) {
    return arr.find(d => d >= x) || arr[arr.length - 1]
  }

answered Mar 27 '21 at 19:22

Tristan Reid

5,844
2
26
31

1

The array must be sorted in ascending order for this to work. – enriquejr99 Sep 20 '22 at 05:28
Yes, based on the sample data I assumed (perhaps incorrectly) that this would be true. The other answer that has a `break` in the loop also makes this assumption; that the first answer found that meets the criteria is correct. – Tristan Reid Sep 22 '22 at 16:15

score 1 · Answer 3 · answered Jul 31 '14 at 14:41

var list = [300, 500, 700, 1000, 2000, 3000];

function findBestMatch(toMatch) {
    // Assumes the array is sorted.

    var bestMatch = null;
    var max = Number.MIN_VALUE;
    var item;

    for (var i = 0; i < list.length; i++) {
        item = list[i];

        if (item > toMatch) {
            bestMatch = item;
            break;
        }

        max = Math.max(max, item);

    }

    //  Compare to null, just in case bestMatch is 0 itself.
    if (bestMatch !== null) {
        return bestMatch;
    }

    return max;

}

alert(findBestMatch(2200));
alert(findBestMatch(3200));

score 0 · Answer 4 · answered Jul 31 '14 at 14:41

 sizesAvailable.sort(function(a, b){return a-b});  // DESCENDING sort

if(upscaleImages)   // do th eif once, not every time through the loop
{
    $.each(sizesAvailable, function()
    {  
        if (this > monitorWidth) 
            sizeToUse = this;
    }
    if (sizeToUse == null) sizeToUse = sizesAvailable[0];
}
else
{
    $.each(sizesAvailable, function()
    {  
        //We don't want to upscale images so....
    }
 }
});

Javascript find closest number in array without going under

4 Answers4

Linked