Binary search a sorted array.

bin_search.es6

function search(dst, arr) {
  
  // sort the input array
  arr.sort((a, b) => a-b);
  
  // if array is reduced to a member and still no match, return false
  if ((arr.length == 1) && (arr[0] !== dst))
    return false;
  
  // define a middlebound
  var middlebound = Math.floor(arr.length / 2);
  
  // if it matches right away, return true
  if (dst == arr[middlebound])
    return true;
  
  // if the dst value is less than the middle value
  if (dst < arr[middlebound]) {
    
    // half the array to the first half
    let lowerbound = 0;
    let upperbound = middlebound;
    return search(dst, arr.slice(lowerbound, upperbound));
  } 
  
  // if the dst value is more than the middle value
  if (dst > arr[middlebound-1]) {
    
    // half the array to the last half
    let lowerbound = middlebound;
    let upperbound = arr.length;
    return search(dst, arr.slice(lowerbound, upperbound));
  }
}

// test it out...
var dst = 90;
var nums = [1, 2, 6, 10, 90, 53, 12, 8, 78, 4];
var included = search(dst, nums);
console.log(included); // -> true