martingale-strategy.js

'use strict';

window.addEventListener('load', () => {
  const txt = document.createElement('span');
  document.body.appendChild(txt);
  const btn = document.createElement('button');
  document.body.appendChild(btn);
  
  let money = 100;
  let target = 101;
  
  let bet = () => Math.min(money, target - money);
  
  btn.textContent = 'Gamble';
  
  let render = () => {
    txt.textContent = `Money: $${money}, Target: $${target}, Bet: $${bet()} `;
  };
  
  render();
  
  btn.addEventListener('click', () => {
    let mul = 2 * Math.round(Math.random()) - 1;
    money += mul * bet();
    
    if (money === target) {
      target += 1;
    }
    
    render();
  });
});