Khan Academy - Binary Search

/* 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 numberOfGuesses = 1;

    while (max >= min) {
        guess = Math.floor((min + max) / 2);

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

        numberOfGuesses++;
    }


    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, 41), 1);
Program.assertEqual(doSearch(primes, 41), 1);