vue: register and import

components/header-nav/menu-nav.vue

<template>
    <div>
        menu nav
    </div>
</template>

components/header-nav/login-nav.vue

<template>
    <div>
        login nav
    </div>
</template>

第一种方法：

components/header-nav/index.js

import MenuNav from "./menu-nav.vue";
import LoginNav from "./login-nav.vue";

export default {MenuNav, LoginNav}

components/header.vue

<template>
  <header>
      <menu-nav></menu-nav>
      <login-nav></login-nav>
  </header>
</template>
<script>
import MenuNav from "./header-nav;
import LoginNav from "./header-nav";
export default {
  components: MenuNav,LoginNav 
};
</script>

第二种方法

<template>
  <header>
      <menu-nav></menu-nav>
      <login-nav></login-nav>
  </header>
</template>
<script>
import MenuNav from "./header-nav/menu-nav.vue";
import LoginNav from "./header-nav/login-nav.vue";
export default {
  components: {MenuNav,LoginNav}
};
</script>