BlueBreeze

A component can be 100% responsible for generating its output, like in this case:

Vue.component('user-name', {
  props: ['name'],
  template: '<p>Hi </p>'
})

or it can also let the parent component inject any kind of content into it, using slots.

What is a slot? It’s a space in your component output that is reserved, waiting to be filled.

You define a slot by putting <slot></slot> in a component template:

Vue.component('user-information', {
  template: '<div class="user-information"><slot></slot></div>'
})

When using this component, any content added between the opening and closing tag will be added inside the slot placeholder:

<user-information>
  <h2>Hi!</h2>
  <user-name name="Flavio"></user-name>
</user-information>

If you put any content side the <slot></slot> tags, that serves as the default content in case nothing is passed in.

A complicated component layout might require a better way to organize content, with multiple slots as well.

This is why Vue offers us named slots.

Named slots

With a named slot you can assign parts of a slot to a specific position in your component template layout, and you use a slot attribute to any tag, to assign content to that slot.

Anything outside any template tag is added to the main slot.

For convenience I use a page single file component in this example:

<template>
  <div>
    <main>
      <slot></slot>
    </main>
    <aside>
      <slot name="sidebar"></slot>
    </aside>
  </div>
</template>

Here is how we can use it, providing the slots content, in a parent component:

<page>
  <template v-slot:sidebar>
    <ul>
      <li>Home</li>
      <li>Contact</li>
    </ul>
  </template>

  <h2>Page title</h2>
  <p>Page content</p>
</page>

There is a handy shorthand, #:

<page>
  <template #sidebar>
    <ul>
      <li>Home</li>
      <li>Contact</li>
    </ul>
  </template>

  <h2>Page title</h2>
  <p>Page content</p>
</page>

Note: Vue 2.6 deprecated the slot attribute in favor of v-slot, and requires it to be added to a template tag (while slot could be applied to any tag)

Scoped slots

In a slot, we can’t access the data contained in the child component from the parent.

Vue recognizes this use case and provides us a way to do so:

<template>
  <div>
    <main>
      <slot v-bind:dogName="dogName"></slot>
    </main>
  </div>
</template>

<script>
export default {
  name: 'Page',
  data: function() {
    return {
      dogName: 'Roger'
    }
  }
}
</script>

In the parent we can access the dog name we passed using:

<page>
  <template v-slot="slotProps">
    
  </template>
</page>

slotProps is just a variable we used to access the props we passed. You can also avoid setting a variable just to hold the props you pass to the child component, by destructuring the object on the fly:

<page>
  <template v-slot="{ dogName }">
    
  </template>
</page>