Simple Binary Search

gistfile1.js

function BinarySearch() {
  this.search = function (needle, haystack) {
    var middle = parseInt(haystack.length/2),
      compareAgainst = haystack[middle];

    if(needle == compareAgainst) { return needle; }
    if(needle < compareAgainst) {  return this.search(needle, haystack.slice(0, middle))}
    if(needle >= compareAgainst) {  return this.search(needle, haystack.slice(middle))}
    return false;
  }
}

b = new BinarySearch();

x = [1,2,3,4,5,6,7,8,9,10,11,12];
console.log(b.search(10, x));