console 命令行工具 X clear

console

document.getElementById("begin").addEventListener("click", function(){
  element1.style.height = '100px';
  element2.style.height = '100px';
  element3.style.height = '100px';
})

<div id="begin">开始</div>

<div id="element1"></div>
<div id="element2"></div>
<div id="element3"></div>

#element1,#element2,#element3{
  width:50px;
  height:50px;
  background-color:red;
  margin:100px;
}