SOURCE

<div class="dispalyFlex flexDemo1">
	<div class="flexItem">1</div>
	<div class="flexItem">2</div>
	<div class="flexItem">3</div>
	<div class="flexItem">4</div>
	<div class="flexItem">5</div>
	<div class="flexItem">6</div>
	<div class="flexItem">7</div>
	<div class="flexItem" style="flex:1">8</div>
<div>

.dispalyFlex{
    display:flex;
    border:1px solid #fff;
    width:400px;
    height:200px;
    box-sizing:border-box;
}

.dispalyFlex .flexItem{
    border:1px solid red;
    width:100px;
    height:30px;
    flex:0 1 auto;
    background:black;
    color:white;
    text-align: center;
}

.flexDemo1{
    flex-direction:column;
    flex-wrap:no-wrap;
    justify-content: flex-start;
    align-items: center;
}