css中设置背景图片适应屏幕

以body为例

body{
	background: url(../img/jld.png) no-repeat center center fixed;
	background-size: cover;
}

.bak{
  background: url(~@/assets/img/Rectangle_9967.png) no-repeat;
    background-size: 100% 100%;
    background-repeat: no-repeat;
}