<style>
      * {
        margin: 0;
        padding: 0;
      }
      .container {
        width: 350px;
        border: 1px solid red;
        display: flex;
        flex-wrap: wrap;
        justify-content: space-between;
      }
      .container::after {
        content: '';
        width: 100px;
      }
      .item {
        width: 100px;
        height: 100px;
        background-color: yellowgreen;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="item"></div>
      <div class="item"></div>
      <div class="item"></div>
      <div class="item"></div>
      <div class="item"></div>
    </div>
  </body>


实现：

　　给父容器添加after伪元素，宽度和子元素宽度保持一致，不要设置高度

效果：

flex布局最后一行元素左对齐_伪元素