How to get the closest element from a javascript array using jQuery?

I have a javascript array like this

var array1= [10,20,30,40,50];

Is there any method using which i can get the closest array element to a given number ? Ex: if i pass 26, It should return 30 ( 26 is closest to 30). If i pass 42, It should return 40.

Any thou开发者_运维问答ghts ? Should i iterate thru each elements ? Is there any methods available for this in jQuery ?

---

Simple with a for loop. No jQuery magic necessary:

function getClosestNum(num, ar)
{
    var i = 0, closest, closestDiff, currentDiff;
    if(ar.length)
    {
        closest = ar[0];
        for(i;i<ar.length;i++)
        {           
            closestDiff = Math.abs(num - closest);
            currentDiff = Math.abs(num - ar[i]);
            if(currentDiff < closestDiff)
            {
                closest = ar[i];
            }
            closestDiff = null;
            currentDiff = null;
        }
        //returns first element that is closest to number
        return closest;
    }
    //no length
    return false;
}

---

If performance is a concern (very large array) and the array is ordered (as in the example), you may want to consider a Binary Search. You can probably find one pre-written for javascript but may need to modify slightly to handle your "closest" piece once the algorithm reaches the end.

---

Because you have ranges of 10 that are sequential, it can be as simple as this:

var array1= [10,20,30,40,50];
var n = 23;
var idx = Math.max( Math.round( n / 10 ) - 1,  0);

Examples:

var array1= [10,20,30,40,50];
var n = 23;
var idx = Math.max( Math.round( n / 10 ) - 1,  0);

alert( array1[ idx ] );   // 20

var n = 28;
var idx = Math.max( Math.round( n / 10 ) - 1,  0);

alert( array1[ idx ] );   // 30

var n = 1;
var idx = Math.max( Math.round( n / 10 ) - 1,  0);

alert( array1[ idx ] );   // 10

Examples: http://jsfiddle.net/GTrNt/

Should work the same with other ranges, like 25:

var array1= [25,50,75,100,125];
var n = 23;
var idx = Math.max( Math.round( n / 25 ) - 1,  0);

alert( array1[ idx ] );   // 25

var n = 48;
var idx = Math.max( Math.round( n / 25 ) - 1,  0);

alert( array1[ idx ] );   // 50

var n = 1;
var idx = Math.max( Math.round( n / 25 ) - 1,  0);

alert( array1[ idx ] );   // 25

Examples: http://jsfiddle.net/GTrNt/1

---

http://jsfiddle.net/nwUbV/1/

With binary search. If it's a really big array though, you'll need to implement a better sorting function such as Quicksort so that performance doesn't suffer.

---

I used jQuery to create the loop (just because I always have jQuery loaded) - it's not really necessary. And this may not be the most efficient method available. But here's a quick function that will do what you need:

var array1 = Array(20, 30, 40, 50);
var closestindex = findClosest(42, array1);
alert('Closest is '+array1[closestindex]);

function findClosest(needle, haystack) {
    var offset = 10000;
    var closest = 0;
    $.each(haystack, function(i) {
        if (haystack[i] <= needle) {
            var localoffset = needle - haystack[i];
        } else {
            var localoffset = haystack[i] - needle;
        }
        if (localoffset <= offset) {
            offset = localoffset;
            closest = i;
        }
    });
    return closest;
}