https://github.com/staltz/callbag-to-awaitable

👜 Use async-await to consume a pullable callbag source
https://github.com/staltz/callbag-to-awaitable

Last synced: 5 days ago
JSON representation

👜 Use async-await to consume a pullable callbag source

• Host: GitHub
• URL: https://github.com/staltz/callbag-to-awaitable
• Owner: staltz
• License: mit
• Created: 2018-02-15T12:45:58.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2018-02-16T17:43:08.000Z (almost 7 years ago)
• Last Synced: 2024-12-24T20:38:16.975Z (20 days ago)
• Language: JavaScript
• Size: 8.79 KB
• Stars: 16
• Watchers: 3
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: readme.js
  • License: LICENSE

Awesome Lists containing this project

• awesome-callbags - to-awaitable

README

        
/**

 * callbag-to-awaitable

 * --------------------

 *

 * Use the `async`/`await` syntax with pullable Callbags! There are actually no

 * Promises in this package, just async-await syntax on objects with a `then`

 * method.

 *

 * `npm install callbag-to-awaitable`

 *

 * Example: on an async pullable callbag source, apply some operators, then

 * convert to an awaitable and consume it in an `async`/`await` function:

 *

 *     const {pipe, take, map} = require('callbag-basics');

 *     const toAwaitable = require('callbag-to-awaitable');

 *

 *     function pullableAsyncSource(start, sink) {

 *       if (start !== 0) return;

 *       let i = 0;

 *       sink(0, t => {

 *         if (t === 1) {

 *           setTimeout(() => { sink(1, i++) }, 1000);

 *         }

 *       });

 *     }

 *

 *     const source = pipe(

 *       pullableAsyncSource, // 0, 1, 2, 3, 4, 5, 6, 7...

 *       take(5), // 0, 1, 2, 3, 4

 *       map(x => x / 4) // 0, 0.25, 0.5, 0.75, 1

 *     );

 *

 *     async function main() {

 *       const next = toAwaitable(source);

 *       try {

 *         while (true) {

 *           const x = await next;

 *           console.log(x);

 *         }

 *       } catch (end) {

 *         console.log('done');

 *       }

 *     }

 *

 *     main()

 *     // 0

 *     // 0.25

 *     // 0.5

 *     // 0.75

 *     // 1

 *     // done

 *

 * For more inquiries, read or fork the source below:

 */

function toAwaitable(source) {

  let talkback;

  let resolve;

  let reject;

  let reason = false;

  source(0, (t, d) => {

    if (t === 0) talkback = d;

    if (t === 1 && resolve) resolve(d);

    if (t === 2) {

      reason = d || true;

      if (reject) reject(reason);

    }

    resolve = void 0;

    reject = void 0;

  });

  return {

    then: (_resolve, _reject) => {

      if (reason) _reject(reason);

      resolve = _resolve;

      reject = _reject;

      if (talkback) talkback(1);

    },

  };

}

module.exports = toAwaitable;