binary search in javascript

binary_search.js

function binarySearch(collection, start, end, target) {
    if(start > end) {
        return;
    }

    var mid = Math.floor( (start + end) / 2 );

    if(collection[mid] > target) {
        return binarySearch(collection, start, mid - 1, target);
    }
    if(collection[mid] < target) {
        return binarySearch(collection, mid + 1, end, target);
    }
    return mid;
}

var ary = [1,2,3,6,7,9,11,234,1231,3233,11111,222222];
var target = 222222;

var index = binarySearch(ary, 0, ary.length, target);
console.log(index);
console.log(target === ary[index]);