binarySearch.js

var binarySearch = function (array, target) {
  var guess, min = 0, max = array.length - 1;

  while(min <= max) {
    guess = Math.floor((min + max) / 2);
    if(array[guess] === target) {
      return guess;
    } else if(array[guess] < target) {
      min = guess + 1;
    } else {
      max = guess - 1;
    }
  }
  return -1;
};