flex制作三列布局 -

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>flex homework</title>
    <style>
      * {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
      }
      body {
        width: 90vw;
        height: 100vh;
        margin: 0 auto;
      }
      .container {
        display: flex;
        outline: 1px solid red;
        flex-flow: row wrap;
        justify-content: space-between;
        align-content: space-between;
        height: 100vh;
      }
      .container > .item:first-of-type,
      .item:last-of-type {
        flex: 0 0 90vw;
        background-color: lightcyan;
        height: 10vh;
        min-height: 80px;
      }
      .container > .item2,
      item3,
      item4 {
        height: 80vh;
        min-height: 400px;
      }
      .container > .item2,
      .item4 {
        flex: 0 0 20vw;
        background-color: lightyellow;
      }
      .container > .item2 {
        justify-content: flex-start;
      }
      .container > .item4 {
        justify-content: flex-end;
      }
      .container > .item3 {
        flex: 1 1 auto;
        background-color: lightred;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="item item1">弹性盒子布局header</div>
      <div class="item item2">left</div>
      <div class="item item3">main</div>
      <div class="item item4">right</div>
      <div class="item item5">footer</div>
    </div>
  </body>
</html>