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mdx-observable

Global state for Markdown documents

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MDX-Observable

alpha project, API may change significantly

0.2.0 does not actually use observables so the name may change 😬

Interactive documents powered by Markdown, React, and Observables

Share state between JSX blocks in a MDX document

  • Declarative React automatically updates observers when data changes
  • Write with Markdown store documents in plain text that can be revision-controlled

Examples

See demos: https://mdx-observable.netlify.com/

git clone git@github.com:alexkrolick/mdx-observable.git
cd mdx-observable
yarn install

Dev Server

Start the dev server with live reloading

yarn run demo:parcel:dev

Static Build

The output files in dist/ can be hosted on a static web server

yarn run build:parcel
// notebook.mdx
import { State, Observe } from 'mdx-observable';

# Counter

<State initialState={{ count: 0 }}>

<Observe>
  {({ setState }) => (
    <button onClick={() => setState(s => ({ count: s.count + 1 }))}>
      Click me
    </button>
  )}
</Observe>

The button has been clicked:

<Observe>
  { ({...state}) => (<span>{state.count} times</span>) }
</Observe>

</State>

Example with a form, table, and graph running in OK-MDX:

screen shot 2018-08-25 at 11 33 32 pm

API

State

State container component

Props:

  • initialState: Object - initial state
  • children: React.Children | function Can either be:
    • React children: JSX or Markdown node(s)
    • A render prop: a single function that gets called with {...state, setState} as the argument

Using render prop

Very similar to React Powerplug's State

Note: whitespace is sensitive in MDX, so the awkward spacing below is important.

<State initialState={{}}>
{({setState, ...state}) => <React.Fragment>

<h1>Hello, World!</h1>

Some markdown

## Some header

- item a
- item b

</React.Fragment>}
</State>

Using context to connect Observe components

<State initialState={{}}>

...child nodes...

<Observe>
  {({ ...state}) => <h1>Hello, World!</h1>}
</Observe>

...more child nodes...

</State>

Observe

Component that re-renders when the global state changes.

Props:

  • children: ({...state, setState}) => React.Node function that accepts an object with:
    • setState: function like React setState, can take an object or an updater function (state => patch); result is shallow merged with current state
    • the rest of the global state
<Observe>
  {({ setState, ...state }) => {
    return <div>{state.something}</div>;
  }}
</Observe>

<Observe>
  {({ setState, something }) => {
    return <div>{something</div>;
  }}
</Observe>

Alternatives

Notebooks

Advantages of MDX-Observable over Jupyter or ObservableHQ:

  • No cells to run; entire document is live
  • Interactivity powered by predictable one-way data flow
  • Use standard JS imports and any React component
  • Produces static bundles
  • Edit using preferred JS tooling
  • Bundle with anything that supports MDX, like Webpack, Gatsby, Parcel, etc.

Other state management libraries for JS

Most state management libraries don't work with MDX because you can't define variables, meaning APIs like const myStore = createStore(); are inaccessible. You can work around this by doing this work in another JS file and importing it, but the logic is hard to follow.

Some renderless/headless libraries thatwork fully inline are:

However the whitespace sensitivity may make them difficult to use.

Roadmap

  • See if <Init /> could work as a wrapper instead of sibling of <Observer />. This would allow better scoping and safer setup/teardown.

  • Some way to define functions inline. This might map well to the concept of "selectors" from Redux. Currently you can work around this gap by defining utilities in external JS files, but this makes it hard to write self-contained notebooks.

Possible API:

<Init state={} selectors={{ selectCheapest: state => {/* compute */} }}>
  • Better live-reload support. MDX utils like ok-mdx do a full remount when the live editor changes or navigation occures; we could add a restoreKey to persist a namespaced cache within the module.

  • Add tests

Potential Issues

Usage outside MDX

Technically mdx-observable doesn't depend on MDX for anything, but since it uses a singleton for a cache, it is not a good fit for state management in an app. Fixed

Warning about blank lines in JSX

Currently (Aug 2018) the MDX parser doesn't allow putting blank lines inside of JSX blocks. If you see an error about "adjacent elements", this is probably why.

License

See LICENSE

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