On: How it feels to learn JavaScript in 2017

[brlewis]

Static? That's half true.

  let planets;
  let planetFilter = planet => true;

The planets variable is static in this example, but planetFilter changes. The "Voila, it works" link near the bottom of the essay leads to a live demo: https://brlewis.github.io/2017/planets.html

Was there a particular aspect of state management you want to hear more about? I'm thinking of a follow-on post. Not sure whether the next one should be state or build system.

[Kiro → brlewis]

Oh, you're right. The state management was so subtle that it actually didn't click when I read it. I don't understand how it knows to rerender though? From what I can tell you're just setting the variable planetFilter and that's it, while with React you would have to do a setState to register it.

[aaron-lebo → Kiro]

You write your templates to handle the state changes, like:

   m('div, {style: `display: ${status ? 'block' : 'none'}`)

Mithril's diffing engine does the rest. If status changes it knows to rerender that section.

[Kiro → aaron-lebo]

But how does Mithril know that status changes? How does it know you just changed the variable?

[pygy_ → Kiro]

By default, Mithril redraws the app after DOM events fire (in this case `onchange={filterHandler(func)}`), and when ajax requests are complete (using the `m.request()` XHR wrapper).

You can also manually trigger a redraw by using `m.redraw()`, but it is rarely needed.