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);

});


});

Answer 1

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/

Answer 2

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));