按钮按下时增加样式效果

demo地址
https://stackblitz.com/edit/js-l96wbs

html

<button class="btn">button</button>

css

.btn {
  width: 60px;
  height: 32px;
  outline: none;
  transition: .5s;
}

.btn:active {
  background-color: #00f;
  color: #fff;
}