JavaScript操作CSS样式和DOM元素

var value = element.style.propertyName;

var fontSize = element.style.fontSize;
//也可以这样设置
element.style.fontSize = 10px;

var value = window.getComputedStyle(element, pseudoElement).propertyName;

var borderWidth = window.getComputedStyle(element).borderWidth;

var classNames = element.classList;

var hasClass = element.classList.contains(className);

element.classList.add(className);
element.classList.remove(className);

element.classList.toggle(className);