binarySearch_iterative.js

/* Returns either the index of the location in the array,
  or -1 if the array did not contain the targetValue */
/* Returns either the index of the location in the array,
  or -1 if the array did not contain the targetValue */
var doSearch = function(array, targetValue) {
  var min = 0;
  var max = array.length - 1;
  var guess;
  var countGuesses = 0;

  while(max >= min) {
    guess = Math.floor((min + max) / 2);
    countGuesses++;
    if (array[guess] === targetValue) {
      
      println(guess);
      println(countGuesses);

      return guess;
    } else if (array[guess] < targetValue) {
      min = guess + 1;
    } else {
      max = guess - 1;
    }
  }  

  return -1;
};

var primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 
    41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97];

var result = doSearch(primes, 73);
println("Found prime at index " + result);

Program.assertEqual(doSearch(primes, 73), 20);
Program.assertEqual(doSearch(primes, 7), 3);
Program.assertEqual(doSearch(primes, 83), 22);