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What’s new in Svelte: March 2021

Call for Svelte Summit Speakers! Improved SSR, non-HTML5 compilation targets, and ESLint TypeScript support

Dani Sandoval

Lots to cover this month with releases from across the Svelte ecosystem. Most importantly, Svelte Summit Spring 2021 has an Open Call for Speakers. The deadline is March 14 so if you have an idea for a talk, submit it now!

Let’s dive into the news 🐬

What’s new in sveltejs/svelte

  • SSR store handling has been reworked to subscribe and unsubscribe as in DOM mode. SSR stores should work much more consistently now (3.31.2, see custom stores and Server-side component API )
  • Multiple instances of the same action are now allowed on an element (3.32.0, example)
  • The new foreign namespace should make it easier for alternative compile targets (like Svelte Native and SvelteGUI) by disabling certain HTML5-specific behaviour and checks (3.32.0, more info)
  • Support for inline comment sourcemaps in code from preprocessors (3.32.0)
  • Destructured defaults are now allowed to refer to other variables (3.33.0, example)
  • Custom elements will now call onMount functions when connecting and clean up when disconnecting (3.33.0, checkout this PR for an interesting conversation on how folks are using Svelte with Web Components)
  • A cssHash option has been added to the compiler options to control the classname used for CSS scoping (3.34.0, docs)
  • Continued improvement to TypeScript definitions

For a complete list of changes, including bug fixes and links to PRs, check out the CHANGELOG

New from sveltejs/language-tools

  • For language server clients that don’t support didChangeWatchedFiles, a fallback file watcher will be used instead
  • New highlighting rules for store accessors and element directives (like bind: and class:)
  • HTML tags can now be renamed together
  • Mustache tags parsing is now more robust and will provide better intellisense in more situations

Haven’t tried the language-tools yet? Check out Svelte Extension for VSCode or find a plugin for your favorite IDE!

Other changes from sveltejs/*

  • eslint-plugin-svelte3 now supports TypeScript as of 3.1.0
  • prettier-plugin-svelte released a number of minor versions to address whitespace and comment trimming issues.
  • svelte-preprocess bug fixes this month include fixes to postcss transformations and support for both v2 and v3 of postcss-load-config
  • sapper‘s 0.29.1 release fixes some bad imports in type definitions, updates typings to be compatible with express/polka, and restores hashing of all CSS file names.

Community Showcase

Apps & Sites

  • Tracking the Coronavirus from NYTimes is an example of SvelteKit in production
  • Budibase is an open-source low-code platform, helping developers and IT professionals build, automate, and ship internal tools 50x faster on their own infrastructure.
  • Track the Parcel is a one-stop tool for tracking parcel status with all major package shippers.
  • Memo is a replacement for email that uses Svelte for modern messaging
  • Userscripts Safari is an open-source userscript editor for Safari... a native Svelte app for Mac OS!
  • SVGX is “the desktop SVG asset manager designers and developers wished they had.”
  • Armoria is a procedural heraldry generator and editor
  • FictionBoard is a virtual table top (VTT) platform that just released fillable and responsive character sheets
  • Castles & Crusades Treasure Generator is a treasure generator for the table top RPG: Castles and Crusades.
  • NESBit Studio is a toolkit to help the development of homebrew NES games
  • ElectroBlocks is an online Arduino IDE with a built-in simulator (Chrome Only)
  • Goblin.life is a 3D world builder whose UI is built with Svelte
  • farmbox is a UAE-based grocery delivery services
  • heroeswearmasks.fun is a client-side machine learning tool that determines whether or not you’re wearing a mask.
  • weatherify is a very pretty (and open source) weather app
  • DSN Live lets you monitor connections between NASA/JPL and interplanetary spacecraft missions in real time.

Demos, Libraries, Tools & Components

  • spc is a special characters picker component for the web
  • svelte-injector lets you inject Svelte components in React, Angular, Vue, jQuery, Vanilla JS.
  • Felte is a form library for Svelte with simple validation reporting.
  • svelte-use-form is form library that “is easy to use and has 0 boilerplate.”
  • Formula provides “Zero Configuration Reactive Forms for Svelte.”
  • Houdini is “the disappearing GraphQL client built for Sapper and Sveltekit.”
  • svelte-split-pane is a draggable split pane component
  • svelte-virtualized-auto-sizer is a high-order component that automatically adjusts the width and height of a single child.
  • svelte-window are components for efficiently rendering large, scrollable lists and tabular data.
  • Svelte Persistent store is a Svelte store that keep its value through pages and reloads
  • Svelte Dark is a VSCode theme inspired by the svelte.dev REPL
  • Import Cost has been updated to support Svelte libraries and help developers keep their bundle size under control.
  • Tree-sitter-svelte provides tree-sitter grammar for svelte
  • Svelte Ripple is a Material Design ripple effect that doesn’t depend on @material/ripple (made by @karakara in the Svelte Discord)
  • Analog SVG Clock is a great example of easing functions (made by @tonmcg in the Svelte Discord)
  • Console Log Styler lets you generate a styled console log using pseudo HTML and CSS (made by @EmNudge in the Svelte Discord)
  • svelte-heroicons is a handy wrapper for the Heroicons icon library
  • supabase-ui-svelte are UI components for Supabase authentication

Have your own Svelte Component to share? Submit your own component to the list of packages on the Svelte Society site.

Learning Resources & Starters

See you next month!

Got something to add? Join us on Svelte Society, Reddit and Discord!