Thermite gives you an API for programmatically live reloading code.

Its main purpose is to act like a library used by development and (experimentally) deployment tools.

I love native browser live code reloading and use it in normal development. Nevertheless there are advantages to doing live code reloading with a library.

• Most runtimes currently do not support live code reloading, so on many browsers, if you want this feature, you're out of luck.
• Browsers that do support this don't offer direct access to this feature from inside your program.

Thermite doesn't have these restrictions.

I'm not complaining about native browser reloading - I think it's great. But I think there's utility in having a library that gives you direct programmatic access to hot code swapping cross browser.

The demo is here.

Check it out!

If you are using Node, first, npm install thermite, then var thermite = require('thermite')

If you are using the browser, use thermite.min.js. thermite is exposed as a global variable. Or just use browserify.

var hotSwappableCode = thermite.eval('(' + function() {
  document.addEventListener("mousemove", function(evt) {
    console.log(evt.clientX * evt.clientY)
  })
} + ')()')

hotSwappableCode.hotSwap('(' + function() {
  document.addEventListener("mousemove", function(evt) {
    console.log(evt.clientX + evt.clientY)
  })
} + ')()')

Calling hotSwap here doesn't add a second event listener to the DOM. It effectively replaces the reference to the event listener stored in the DOM with a new one.

Thermite works by rewriting code and proxying each function.

Additionally it stores the initial version of your code in a map.

When you call hotSwap, thermite runs a diff to identify how functions change. It uses this diff to update the map.

Whenever a function runs, it checks its version. When a function finds that its version is lower than the one in the map, it evals the new function (creating it in the proper scope).

MIT