https://github.com/staltz/callbag-merge

👜 Callbag factory that merges data from multiple callbag sources
https://github.com/staltz/callbag-merge

Last synced: about 2 months ago
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👜 Callbag factory that merges data from multiple callbag sources

• Host: GitHub
• URL: https://github.com/staltz/callbag-merge
• Owner: staltz
• License: mit
• Created: 2018-01-23T21:33:19.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2019-04-10T09:19:02.000Z (over 5 years ago)
• Last Synced: 2024-07-20T20:47:40.155Z (2 months ago)
• Language: JavaScript
• Homepage:
• Size: 26.4 KB
• Stars: 8
• Watchers: 3
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: readme.js
  • License: LICENSE

Awesome Lists containing this project

• awesome-callbags - merge

README

        
/**

 * callbag-merge

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

 *

 * Callbag factory that merges data from multiple callbag sources. Works well

 * with listenable sources, and while it may work for some pullable sources,

 * it is only designed for listenable sources.

 *

 * `npm install callbag-merge`

 *

 * Example:

 *

 *     const interval = require('callbag-interval');

 *     const forEach = require('callbag-for-each');

 *     const merge = require('callbag-merge');

 *

 *     const source = merge(interval(100), interval(350));

 *

 *     forEach(x => console.log(x))(source); // 0

 *                                           // 1

 *                                           // 2

 *                                           // 0

 *                                           // 3

 *                                           // 4

 *                                           // 5

 *                                           // ...

 */

function merge(...sources) {

  return (start, sink) => {

    if (start !== 0) return;

    const n = sources.length;

    const sourceTalkbacks = new Array(n);

    let startCount = 0;

    let endCount = 0;

    let ended = false;

    const talkback = (t, d) => {

      if (t === 2) ended = true;

      for (let i = 0; i < n; i++) sourceTalkbacks[i] && sourceTalkbacks[i](t, d);

    };

    for (let i = 0; i < n; i++) {

      if (ended) return;

      sources[i](0, (t, d) => {

        if (t === 0) {

          sourceTalkbacks[i] = d;

          if (++startCount === 1) sink(0, talkback);

        } else if (t === 2 && d) {

          ended = true;

          for (let j = 0; j < n; j++) {

            if (j !== i) sourceTalkbacks[j] && sourceTalkbacks[j](2);

          }

          sink(2, d);

        } else if (t === 2) {

          sourceTalkbacks[i] = void 0;

          if (++endCount === n) sink(2);

        } else sink(t, d);

      });

    }

  };

}

export default merge;