在Javascript中实现像addClass、removeClass和delay这样的jquery函数

function addClass(element, className) {
  if (element.classList) {
    element.classList.add(className);
  } else {
    element.className += ' ' + className;
  }
}

function removeClass(element, className) {
  if (element.classList) {
    element.classList.remove(className);
  } else {
    element.className = element.className.replace(new RegExp('(^|\\b)' + className.split(' ').join('|') + '(\\b|$)', 'gi'), ' ');
  }
}

function delay(func, delayTime) {
  setTimeout(func, delayTime);
}