Unlock the Power of Reusable Components in Svelte
When building UI applications, creating reusable components is crucial for maintaining a clean and efficient codebase. One way to achieve this is by passing children elements or components to parent components. In Svelte, we can leverage slots to create components that accept and render any children, making them highly reusable.
What are Svelte Slots?
Svelte slots allow us to pass child data and content to parent components, making them reusable across our application. This approach helps keep our codebase DRY (Don’t Repeat Yourself) and makes maintaining, debugging, and updating components easier.
Practical Applications of Slots
Let’s create a Card component that accepts child data and content. We can use the Card component in App.svelte and pass in our content:
svelte
<Card>
<h1>Card Title</h1>
<p>Card Content</p>
</Card>
Slot Fallbacks: Adding Default Content
We can add fallback content to slots to act as placeholders when the slots are empty. For example, if we create a blog post card component, we may want to add a fallback title to each post until the cards receive the actual data.
svelte
<Card>
<slot fallback="Fallback Blog Title"> </slot>
</Card>
Named Slots: Extending Component Functionality
We can have multiple slots in a Svelte component by using the name attribute on the slot component. Let’s extend the blog card component to include a title, date, and content section:
svelte
<Card>
<slot name="title"> </slot>
<slot name="date"> </slot>
<slot name="content"> </slot>
</Card>
Using Svelte Fragments to Avoid Unnecessary HTML Elements
When passing multiple components into a named slot, we can use svelte:fragment to avoid adding unnecessary HTML elements that can affect the layout and styling.
svelte
<Card>
<slot name="header">
<svelte:fragment>
<h1>Card Title</h1>
<p>Card Date</p>
</svelte:fragment>
</slot>
</Card>
Conditionally Displaying Slots
We can use the special $$slots variable to conditionally display slots based on whether they contain content. This ensures that empty slots do not render and affect the layout and styling of our application.
svelte
<Card>
{#if $$slots.title}
<slot name="title"> </slot>
{/if}
</Card>
Passing Data Across Slots through Props
We can use slot props to pass data from the child to parent using the let: directive of slots. This helps us set up separation of concerns between the parent and child component.
svelte
<Contacts let:employees={employees}>
{#each employees as employee}
<Card>
<slot name="title">{employee.name}</slot>
<slot name="content">{employee.bio}</slot>
</Card>
{/each}
</Contacts>
By mastering Svelte slots, you can create reusable components that are flexible, efficient, and easy to maintain. Take your Svelte skills to the next level and start building amazing applications today!