效果：

代码：

html：

<div id="all">
  <div id="drawer"></div>
  <div id="main">
    <div id="nav">
      <div id="open"></div>
    </div>
    <div id="content"></div>
    <div id="mask"></div>
  </div>
</div>

css：

#all{
  position:absolute;
  top:50%;
  left:50%;
  transform:translate(-50%,-50%);
  background:#ddd;
  width:300px;
  height:500px;
  overflow:hidden;
}
#drawer{
  position:absolute;
  width:200px;
  height:500px;
  background:skyblue;
  top:0;
  left:-200px;
  transition:all 0.5s;
}
#main{
  position:absolute;
  width:300px;
  height:500px;
  background:tomato;
  top:0;
  left:0;
  transition:all 0.5s;
}
#nav{
  height:50px;
  background:yellow;
  position:relative;
}
#open{
  background:tomato;
  width:35px;
  height:35px;
  position:absolute;
  top:50%;
  left:10px;
  transform:translate(0,-50%);
  cursor:pointer;
}
#mask{
  display:none;
  position:absolute;
  width:300px;
  height:500px;
  top:0;
  background:rgba(0,0,0,.5);
}

javascript：

var drawer = document.getElementById("drawer");
var main = document.getElementById("main");
var mask = document.getElementById("mask");
document.getElementById("open").onclick = function(){
  drawer.style.left = 0; 
  main.style.left = 200 + "px"; 
  mask.style.display = "block";
}
mask.onclick = function(){
  drawer.style.left = -200 + "px"; 
  main.style.left = 0; 
  mask.style.display = "none";
}