Binary Search

binarysearch.js

/* 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 guessCount = 0;
    while (max >= min) {
        guessCount ++;
        guess = Math.floor((min + max)/2);
        println(guess);
        if (array[guess] === targetValue) {
            println(guessCount);
            return guess;
        }
        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, 61), 17);
Program.assertEqual(doSearch(primes, 13), 5);