div宽度随屏幕大小变化

<div class="box">
    <div class="left"></div>
    <div class="right"></div>
</div>

.box{
    display: flex;
    display: -webkit-flex;
    flex-direction: row;
    align-items: center;
    border: 1px solid #c3c3c3;
}

.left {
    flex-basis：100px;
    -webkit-flex-basis: 100px;   /* Safari 6.1+ */
    background-color: red;
    height: 100%;
 
}

.right {
    background-color: blue;
    flex-grow: 1;
}

<div class="left"></div>
<div class="right"></div> 

*{
    margin: 0;
    padding: 0;
}

.left {
    float: left;
    width: 220px;
    background-color: green;
}

.right {
    background-color: orange;
    margin-left: 220px;    /*==等于左边栏宽度==*/
}