How Can I Determine Which Array Index My Number Is Closest To?

I have an array and var that look like this: var paymentMilestones = [0, 30, 60, 90]; var daysOverdue = 33; In JavaScript, how can I programmatically determine which of the paymen

Solution 1:

A quick answer (if there is a tie it will bring back both - assuming the array is pre-sorted):

var paymentMilestones = [0, 30, 60, 90];
var daysOverdue = 33;

function findClose(array,elem){
    var minDelta = null;
    var minIndex = null;
    for (var i = 0 ; i<array.length; i++){
        var delta = Math.abs(array[i]-elem);
        if (minDelta == null || delta < minDelta){
            minDelta = delta;
            minIndex = i;
        }
        else if (delta == minDelta) {
            return [array[minIndex],array[i]];
        }
        // unchecked: stop if delta starts becoming bigger again
        else { 
            return [array[i-1]];
        }


    }
    return array[minIndex];
}
var closest = findClose(paymentMilestones,daysOverdue);