1.0.0 • Public • Published


BuckleScript bindings for Most.js.

In Reason:

let add = (x, y) => x + y;
let isEven = x => x mod 2 === 0 |> Js.Boolean.to_js_boolean;
  fromList([0, 1, 2, 3, 4, 5, 6, 7, 8])
  |> map(add(2))
  |> filter(isEven)
  |> observe(x => Js.log(x))
  |> Js.Promise.then_((_) => {
       Js.log("Stream completed");
 * Logs:
 * 2
 * 4
 * 6
 * 8
 * 10
 * Stream completed

An example of implementing the Redux architecture in a ReasonReact project can be seen here.

How do I install it?

Inside of a BuckleScript project:

npm install --save bs-most

Then add bs-most to your bs-dependencies in bsconfig.json:

  "bs-dependencies": [

How do I use it?

The Most.js API docs are probably the best source of information about each method. This library attempts to provide very low-level bindings, except for what's noted in the What's different section.

The bindings are a single file in src/ I try to provide comments next to each binding and am working on flushing out tests so that users can refer to them.

I am also available by e-mail or DM on the Reason discord (username: @lilactown).

What's missing

  1. generate - Reason doesn't have generator support yet
  2. transduce - Awkward to use in Reason/OCaml without a solid transducer impl (maybe coming soon?? 😉)
  3. combineArray - the callback for this is variadic (depending on how many streams you have in the array), not sure how to type it yet 😞

What's different

  1. Predicates that normally return "truthy" values, now only accept returning booleans
  2. sample is variadic so we offer sample1, sample2, sample3... sample6
  3. fromEvent - DOM events are supported, but generic EventEmitter's are not yet
  4. from only works on arrays right now; generic iterators must be coerced
  5. fromList is a function that creates a stream from a Reason List type, e.g. fromList([1, 2, 3])
  6. unfold is modeled a bit differently - instead of taking in a JS object { done, value, seed }, it takes an option (value, seed). Example:
/* emits 2,4,6 then completes */
  (seed) =>
    if (seed < 4) {
      let nextSeed = seed + 1;
      Some((seed * 2, nextSeed));
    } else {


This library also includes some bindings for Subjects. Subjects are very useful for e.g. implementing a state store/dispatch system. The API is a little bit different from the raw most-subject library:

  • Subject.make: creates an asynchronous Subject
  • Subject.asStream: casts a subject to a stream, to be used by the rest of the Most module
  • emits a value on a subject
  • Subject.error: emits an error on a subject
  • Subject.complete: completes a subject with no value
  • Subject.completeWith: completes a subject with a value


npm run build

Build + Watch

npm run watch


npm run test

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npm i bs-most

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  • lilactown