binary_search

var input = [1,2,3,4,5,6,7,8,9];

var bs = function(input){
  var middleIndex = Math.ceil(input.length/2) - 1;
  var middle = input[middleIndex];

  var target = 6;

  //base
  if(middle === target){
    return true;
  }else if(middle < target){
    return bs( input.slice(middleIndex+1) );
  }else{
    return bs( input.slice(0, middleIndex) );
  }
}

var output = bs(input);

console.log('output', output);