<template>
  <div class="layout-box">
    <div class="left">左侧侧边栏</div>
    <div class="right">右侧头部</div>
  </div>
</template>
<style scoped lang='scss'>
.layout-box {
    display: flex;
    height: 100vh;
    .left {
        width: 300px;
        background: red;
    }
    .right {
        width: calc(100% - 300px);
        background: blue;
    }
}
</style>