CSS弹性盒模型flex在布局中的使用方法

<style>.parent{
    display: flex;
    justify-content: center;
    align-items: center;}</style>
<div class="parent"  style="background-color: lightgrey; height: 100px; width: 200px;">
    <div class="in" style="background-color: lightblue;">DEMO</div>      </div>

<style>.parent{
    display: flex;}.in{
    margin: auto;}</style>
<div class="parent"  style="background-color: lightgrey;height: 100px;width: 200px;">
    <div class="in" style="background-color: lightblue;">DEMO</div>      </div>

<style>.parent{
   display: flex;    
   justify-content:space-between
   }
</style>
<div class="parent"  style="background-color: lightgrey;height: 100px;width: 200px;">
    <div class="in" style="background-color: lightblue;">DEMO</div>
    <div class="in" style="background-color: lightgreen;">DEMO</div>
    <div class="in" style="background-color: lightcyan;">DEMO</div>    
    <div class="in" style="background-color: lightseagreen;">DEMO</div>     
 </div>

<style>.parent{
    display: flex;
    align-items: flex-end;
    }
</style>
<div class="parent"  style="background-color: lightgrey;height: 100px;width: 200px;">
    <div class="in" style="background-color: lightblue; height:20px;">DEMO</div>
    <div class="in" style="background-color: lightgreen; height:30px;">DEMO</div>
    <div class="in" style="background-color: lightcyan; height:40px;">DEMO</div>
    <div class="in" style="background-color: lightseagreen; height:50px;">DEMO</div>      
</div>

<style>.inputBox{
    display: flex;
    width: 250px;}.inputBox-ipt{
    flex: 1;}
</style>
<div class="inputBox">
  <input class="inputBox-ipt">
  <button class="inputBox-btn">按钮</button>
</div>

<style>body,p{margin: 0;}.parent{
    display: flex;}.child{
    flex:1;
    height: 100px;}.child + .child{
    margin-left: 20px;}
</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="child" style="background-color: lightblue;">1</div>
    <div class="child" style="background-color: lightgreen;">2</div>
    <div class="child" style="background-color: lightsalmon;">3</div>
    <div class="child" style="background-color: pink;">4</div>                
</div>

<style>p{margin: 0;}.parent{display: flex;}.left,.center{margin-right: 20px;}.right{flex: 1;}</style>
<div class="parent" style="background-color: lightgrey;">
    <div class="left" style="background-color: lightblue;">
        <p>left</p>
        <p>left</p>
    </div>            
    <div class="center" style="background-color: pink;">
        <p>center</p>
        <p>center</p>
    </div>            
    <div class="right"  style="background-color: lightgreen;">
        <p>right</p>
        <p>right</p>
    </div>                    
</div>

<style>        
     .box{
    display: flex;
    background-color: lightgrey;
    width: 300px;}.left{
    margin-right: 20px;
    background-color: lightblue;
    height: 30px;}.main{
    flex:1;}
 </style>
<div class="box">
    <div class="left">左侧悬挂</div>
    <div class="main">主要内容主要内容主要内容主要内容主要内容主要内容主要内容主要内容主要内容主要内容主要内容主要内容主要内容</div>    
</div>

<style>body,p{margin: 0;}body,html,.parent{height: 100%;}.parent{
    display: flex;
    flex-direction: column;}.top,.bottom{
    height: 50px;}.middle{
    display: flex;
    flex: 1;}.left{
    width: 100px;
    margin-right: 20px;}.right{
    flex: 1;
    overflow: auto;}.right-in{
    height: 1000px;}</style>
<div class="parent" id="parent" style="background-color: lightgrey;">
    <div class="top" style="background-color: lightblue;">
        <p>top</p>
    </div> 
    <div class="middle" style="background-color: pink;">
        <div class="left" style="background-color: orange;">
            <p>left</p>
        </div>     
        <div class="right" style="background-color: lightsalmon;">
            <div class="right-in">
                <p>right</p>
            </div>            
        </div>                    
    </div>              
    <div class="bottom" style="background-color: lightgreen;">
        <p>bottom</p>
    </div>        
</div>