Coin toss probability simulator

cointoss-prob-sim.js

/**
 * "What is the probability of getting
 *  7 tails in a row, out of 150 tosses
 *  of a fair coin?"
 */

function experiment(streak, tosses) {
  var i, ctr = 0;
  for (i = 0; i < tosses; i++) {
    if (Math.random() < 0.5) ctr = 0;
    else if (++ctr === streak) return 1;
  }
  return 0;
}

function run(streak, tosses, runs) {
  var i, total = 0;
  for (i = 0; i < runs; i++) {
    total += experiment(streak, tosses);
  }
  return total / runs;
}

console.log('\nP(A) = %s\n',
  run(7, 150, 1e6));