text: document.addEventListener("DOMContentLoaded", loadPage);
  
  function loadPage() {
  	dom.loginButton = one("#login-signup-button");
  	dom.usernameInput = one("#username");
  	dom.passwordInput = one("#password");
  	dom.usernameInput.onchange = validateLoginButton;
  	dom.passwordInput.onchange = validateLoginButton;
  	dom.usernameInput.oninput = validateLoginButton;
  	dom.passwordInput.oninput = validateLoginButton;
  	validateLoginButton();
  }
  
  function isEmpty(str) {
  	return (str.length === 0 || !str.trim());
  }
  
  function validateLoginButton() {
  	var validLogin = !isEmpty(dom.usernameInput.value) && !isEmpty(dom.passwordInput.value);
  	dom.loginButton.disabled = !validLogin;
  }