TVKit

A proxy server which allows using modern dev servers in old browsers. "Run SvelteKit on a TV"

TVKit intercepts requests to a webserver and converts the responses to make them work in old browsers. This works by injecting polyfills and transpiling the modern JavaScript and CSS to code that's compatible with older browsers.

Usage (dev server)

• Start your vite project as normal
• Run npx tvkit@latest serve --browser "chrome 50" in another terminal
• Open http://localhost:3000/ in an old browser to visit your website

tvkit serve

Option	Default value	Description
[target]	http://localhost:5173	The URL of the website that is too new
--port	3000	The port the proxy server is going to run on
--browser		The transpilation target (uses browserslist)
--add		Override feature. Ex --add "es6-module" forces adding systemjs polyfill
--remove		Override feature: Ex --remove fetch forces omitting whatwg-fetch polyfill
--no-css	false	Disable CSS transpilation
--ssl-cert		Path to the SSL certificate for https
--ssl-key		Path to the SSL certificate's private key
--no-minify	false	Disable minificaton for the polyfills
--help		Show message per command. Ex: tvkit serve --help

TVKit adds browser aliases for SmartTV platforms: Example --browser "Tizen 5" is aliased to Chrome 63

Start tvkit & servers at the same time

Use concurrently to start both servers at the same time:

// package.json
"scripts": {
  "dev": "concurrently --kill-others-on-fail \"npm:dev:*\"",
  "dev:vite": "vite dev",
  "dev:tvkit": "tvkit serve --browser \"Tizen 4, WebOS 4\"",

Usage (build)

Copy folder contents and transform all html, js & css files into new directory.

Build your project for modern browsers (example: vite build) and then use the tvkit build to convert the generated folder into something that is compatible for older browsers.

npx tvkit@latest build path/to/build --out path/to/output --browser "chrome 50"

tvkit build

Option	Default value	Description
[folder]		The folder containing modern javascript
--out		The output folder
--browser		The transpilation target (uses browserslist)
--force	false	Overwrite files in output folder
--add		Override feature. Ex --add "es6-module" forces adding systemjs polyfill
--remove		Override feature: Ex --remove fetch forces omitting whatwg-fetch polyfill
--no-css	false	Disable CSS transpilation
--no-minify	false	Disable minificaton
--quiet	false	Only log errors
--help		Show message per command. Ex: tvkit build --help

Note: Polyfilling will degrade the performance for platforms that could've run the modern javascript version. An alternative to tvkit build is using @vitejs/plugin-legacy which has better performance on modern browsers, but doesn't work for some project setups (like SvelteKit projects).

TVKit supports static builds from any framework and has special support for SvelteKit's node-adapter & vercel-adapter builds.

Technology

• SystemJS to polyfill ES modules.
• Babel to transpile javascript on the fly.
• core-js, whatwg-fetch and others to polyfill missing features.
• PostCSS to transpile CSS on the fly using postcss-preset-env.
• And others: Rollup, Acorn, Terser, Yargs

Consider funding these projects as they do a lot of the heavy lifting.