코드 :

function array_binarySearch(narray, delement) {
   var mposition = Math.floor(narray.length / 2);

   if (narray[mposition] === delement){
      return mposition;
   }
   else if (narray.length === 1) 
   {
      return null;
   }
   else if (narray[mposition] < delement) {
      var arr = narray.slice(mposition + 1);
      var res = array_binarySearch(arr, delement);
      if (res === null)
      {
         return null;
      }
      else {
         return mposition + 1 + res;
      }
   }
   else {
      var arr1 = narray.slice(0, mposition);
      return array_binarySearch(arr1, delement);
   }
}

 var myArray = [1, 2, 3, 5, 6, 7, 10, 11, 14, 15, 17, 19, 20, 22, 23];
 console.log(array_binarySearch(myArray, 6));

결과 : 

4