主轴为垂直方向时的项目排列

<!-- flex-direction使用 -->
    <div class="container">
        <div class="item">1</div>
        <div class="item">2</div>
        <div class="item">3</div>
    </div>

.container{
            width: 300px;
            height: 150px;
            display: flex;
            /* 主轴方向：默认为行 */
            flex-direction: row;
            flex-direction: column;
            /* 项目二边分配 */
            justify-content: flex-start;
            justify-content: flex-end;
            justify-content: center;
            /* 项目之间分配 */
            justify-content: space-between;
            justify-content: space-around;
            justify-content: space-evenly;
        }
    </style>