How to Create Svelte Component Libraries with SvelteKit

Read if:

You have basic understanding of SvelteKit.
Wanna learn best thing about SvelteKit

Complete Example:

Link for live example on stackblitz

Introduction
I love SvelteKit, there are many reasons for that but on of them is svelte-kit inbuilt packaging module.

The SvelteKit documentation states that you can use the SvelteKit to build component libraries as well as apps. So I'm going to tell you every single step including publishing the package to npm.

Setting Up SvelteKit

Steps to create your SvelteKit project MyComponentsLibrary



~ npm init svelte@next MyComponentsLibrary
~ cd MyComponentsLibrary
~ npm i
~ npm run dev

Current project tree

As you can see above dir tree there is one folder inside src named lib. This is the place where you going to make your components.

Now make a Button.svelte and index.js file in lib directory. Which will going to look like this:

As you can see i have added both the file and now we gonna make our Button Component.

Code Button.svelte



<script lang="ts">
    export let label = '';
    export let disabled = false;
    let props = { ...$$restProps };
</script>

<button class={props.class} {disabled} style={props.style} props on:click on:*>
    {label}
    <slot />
</button>

Now, I'll explain what's happening here :

As you can see we are using export let label, this line means where we use Button component we can pass label value in that. same for disabled.
{ ...$$restProps } this is a special thing in SvelteKit. If you pass extra parameter to component you can access them using this inside the component. As you can in button tag where I'm passing style and classes to it.
<slot /> means what ever you write between your component tag will be render on the web page.

Now we are done with Button.svelte.

Code index.js



export { default as Button } from './Button.svelte';

This line means be gonna export Button as Button from Button.svelte file.

Setting Up package.json

First assign name like this "name": "svexy-ui". This will be the package name of your library.
Add exports like "exports": { ".": "./index.js" }. This is root file.
Add module like "module": "index.js". This is main file.

For more info please google them exports in package.json and module in package.json.

Setting Up svelte.config.js

Add package: { dir: 'folder that will be generated' } in kit.

You can find all code in the live example.

Packaging on our components

First install svelte2tsx using npm.
Second run this npm run package in your terminal. This will generate a dir in root of the project.

In image you can see it generated a folder by the name svexy-ui. This contains you package that you can publish on npm.It contains your index.js file with lib directory files with package.json and with a README.md.

Publishing to NPM

If you are ready you can publish it on npm. You must log in to npm from your terminal using npm login.

Change the directory to package and run npm publish command.



cd svexy-ui
npm publish --access public

...
That's all we have to do and you gonna have your svelte component library on npm.

Resources

This is me writing for you. If you wanna ask or suggest anything please put it in comment.