JavaScript solution for http://codecombat.com/play/level/danger-minefield level

danger-minefield.js

var coin, firstMineIndex, lastMineIndex, pr;

this.detonate = function(i) {
  return this.say("Detonate " + i, [i]);
};

firstMineIndex = 2;

lastMineIndex = 120;

function eratosthenes(limit) {
    var primes = [];
    if (limit >= 2) {
        var sqrtlmt = Math.sqrt(limit) - 2;
        var nums = new Array(); // start with an empty Array...
        for (var i = 2; i <= limit; i++) // and
            nums.push(i); // only initialize the Array once...
        for (var i = 0; i <= sqrtlmt; i++) {
            var p = nums[i]
            if (p)
                for (var j = p * p - 2; j < nums.length; j += p)
                    nums[j] = 0;
        }
        for (var i = 0; i < nums.length; i++) {
            var p = nums[i];
            if (p)
                primes.push(p);
        }
    }
    return primes;
}

pr = eratosthenes(lastMineIndex);
__indexOf = [].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; };

for (i = firstMineIndex; i <= lastMineIndex ; i++) {
  if (__indexOf.call(pr, i) < 0) {
    this.detonate(i);
  }
}

this.say("Woohoo, safe! Lootin' time!");

coins = this.getItems();
for (var i = 0; i < coins.length; i++) {
  this.move(coins[i].pos);
}