js get 元素
-document.write
-document.getElementById
-obj.style.property(property: backgroundColor,color,height,weight,font,fontfamily,fontsize)
-obj.style.dislay(display: none,block)
-obj.innerHTML
-obj.className
-优先级:算术操作符>比较操作符>逻辑操作符>赋值操作符(=)
事件:
-onClick
-onmouseover
-onmouseout
-onfocus
-onblur