"What's new in Svelte" December newsletter (sveltejs#5706)

site/content/blog/2020-12-01-whats-new-in-svelte-december-2020.md

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+---
+title: What's new in Svelte: December 2020
+description: Better tooling, export maps and improvements to slots and context
+author: Daniel Sandoval
+authorURL: https://desandoval.net
+---
+
+It's the last "What's new in Svelte" of the year and there's lots to celebrate! This month's coverage includes updates from `rollup-plugin-svelte`, `Sapper` and `SvelteKit` and a bunch of showcases from the Svelte community!
+
+## New features & impactful bug fixes
+
+1. `$$props`, `$$restProps`, and `$$slots` are all now supported in custom web components (**3.29.5**, [Example](https://svelte.dev/repl/ad8e6f39cd20403dacd1be84d71e498d?version=3.29.5)) and  `slot` components now support spread props: `<slot {...foo} />` (**3.30.0**)
+2. A new `hasContext` lifecycle function makes it easy to check whether a `key` has been set in the context of a parent component (**3.30.0** & **3.30.1**, [Docs](https://svelte.dev/docs#hasContext))
+3. `SvelteComponent` is now typed which makes it easier to add typed classes that extend base Svelte Components. Component library and framework authors rejoice! An example: `export class YourComponent extends SvelteComponent<{aProp: boolean}, {click: MouseEvent}, {default: {aSlot: string}}> {}` (**3.30.0**, [RFC](https://github.com/sveltejs/rfcs/pull/37))
+4. Transitions within `{:else}` blocks should now complete successfully (**3.29.5**, [Example](https://svelte.dev/repl/49cef205e5da459594ef2eafcbd41593?version=3.29.5))
+5. Svelte now includes an export map, which explicitly states which files can be imported from its npm package (**3.29.5** with some fixes in **3.29.6**, **3.29.7** and **3.30.0**)
+6. `rollup-plugin-svelte` had a new [7.0.0 release](https://github.com/sveltejs/rollup-plugin-svelte/blob/master/CHANGELOG.md). The biggest change is that the `css` option was removed. Users who were using that option should add another plugin like `rollup-plugin-css-only` as demonstrated [in the template](https://github.com/sveltejs/template/blob/5b1135c286f7a649daa99825a077586655051649/rollup.config.js#L48)
+
+
+## What's going on in Sapper?
+Lots of new TypeScript definition improvements to make editing Sapper apps even easier! CSS for dynamic imports also should now work in `client.js` files. (Unreleased)
+
+## What's the deal with SvelteKit?
+We're glad you asked! If you didn't catch Rich's blog post from early last month, [you can find it here](https://svelte.dev/blog/whats-the-deal-with-sveltekit)!
+
+For all the features and bugfixes see the CHANGELOGs for [Svelte](https://github.com/sveltejs/svelte/blob/master/CHANGELOG.md) and [Sapper](https://github.com/sveltejs/sapper/blob/master/CHANGELOG.md).
+
+---
+
+## Community Showcase
+
+**Apps & Sites**
+- [narration.studio](https://narration.studio/) (Chrome Only) is an automatic in-browser audio recording & editing platform for voice over narration.
+- [Vippet](https://vippet.netlify.app/) is a video recording and editing tool for the browser.
+- [Pattern Monster](https://pattern.monster/) is a simple online pattern generator to create repeatable SVG patterns.
+- [Plant-based diets](https://planetbaseddiets.panda.org/) is a website from the World Wildlife Foundation (WWF) built with Svelte.
+- [johnells.se](https://www.johnells.se/) is a Swedish fashion e-commerce site, built with [Crown](https://crownframework.com/) - a Svelte-powered framework.
+- [sentence-length](https://sentence-length.netlify.app/) is a learning and analysis tool to show how some authors play with different lengths, while others stick with one.
+- [svelte-presenter](https://github.com/stephane-vanraes/svelte-presenter) lets you quickly make good looking presentations using Svelte and mdsvex.
+
+**Demos**
+- [u/loopcake got SSR working in Java Spring Boot](https://www.reddit.com/r/sveltejs/comments/jkh5up/svelte_ssr_but_its_java_spring_boot_and_its_native/) for all the Java shops out there looking to render Svelte server-side.
+- [svelte-liquid-swipe](https://github.com/tncrazvan/svelte-liquid-swipe) shows off a fancy interaction pattern using svg paths.
+- [Crossfade Link Animation](https://svelte.dev/repl/7f68e148caf04b2787bb6f296208f870?version=3.29.7) demonstrates how to animate between navigation links using a crossfade (made by Blu, from the Discord community)
+- [Clip-Path Transitions](https://svelte.dev/repl/b5ad281ae8024b629b545c70c9e8764d?version=3.29.7) showcases how to use clip paths and custom transitions to create magical in-and-out transitions (made by Faber, from the Discord community)
+
+**Learning Resources**
+- [lihautan](https://www.youtube.com/channel/UCbmC3HP3FaAFdcZkui8YoMQ/featured) has been making easy-to-follow videos to share his in-depth knowledge of Svelte.
+- [Lessons From Building a Static Site Generator](https://nicholasreese.com/lessons-from-building-a-static-site-generator/) shares the backstory and thinking behind Elder.js - and the design decision made along the way.
+- [Svelte Tutorial and Projects Course ](https://www.udemy.com/course/svelte-tutorial-and-projects-course/) is a udemy course by John Smilga where students learn Svelte.js by building interesting projects.
+- [Building Pastebin on IPFS - with FastAPI, Svelte, and IPFS](https://amalshaji.wtf/building-pastebin-on-ipfs-with-fastapi-svelte-and-ipfs) explains how to make a distributed pastebin-like application.
+
+
+**Components, Libraries & Tools**
+- [svelte-crossword](https://russellgoldenberg.github.io/svelte-crossword/) is a customizable crossword puzzle component for Svelte.
+- [svelte-cloudinary](https://github.com/cupcakearmy/svelte-cloudinary) makes it easy to integrate Cloudinary with Svelte (including Typescript and SSR support)
+- [Svelte Nova](https://extensions.panic.com/extensions/sb.lao/sb.lao.svelte-nova/) extends the new Nova editor to support Svelte
+- [saos](https://github.com/shiryel/saos) is a small svelte component to animate your elements on scroll.
+- [Svelte-nStore](https://github.com/lacikawiz/svelte-nStore) is a general purpose store replacement that fulfills the Svelte store contract and adds getter and calculation features.
+- [svelte-slimscroll](https://github.com/MelihAltintas/svelte-slimscroll) is a Svelte Action that transforms any div into a scrollable area with a nice scrollbar.
+- [svelte-typewriter](https://github.com/henriquehbr/svelte-typewriter) is a simple and reusable typewriter effect for your Svelte applications
+- [svelte-store-router](https://github.com/zyxd/svelte-store-router) is a store-based router for Svelte that suggests that routing is just another global state and History API changes are just an optional side-effects of this state.
+- [Routify](https://routify.dev/blog/routify-2-released) just released version 2 of its Svelte router.
+- [svelte-error-boundary](https://www.npmjs.com/package/@crownframework/svelte-error-boundary) provides a simple error boundary component for Svelte that can be can be used with both DOM and SSR targets.
+- [svelte2dts](https://www.npmjs.com/package/svelte2dts) generates d.ts files from svelte files, creating truly sharable and well typed components.
+
+## See you next month!
+
+Got an idea for something to add to the Showcase? Want to get involved more with Svelte? We're always looking for maintainers, contributors and fanatics... Check out the [Svelte Society](https://sveltesociety.dev/), [Reddit](https://www.reddit.com/r/sveltejs/) and [Discord](https://discord.com/invite/yy75DKs) to get involved!
+
+That's all for the year, folks! See you in January 😎