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

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

Last synced: 5 days ago
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👜 Callbag factory that concatenates data from multiple callbag sources

• Host: GitHub
• URL: https://github.com/staltz/callbag-concat
• Owner: staltz
• License: mit
• Created: 2018-01-26T17:03:59.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2019-02-11T11:24:47.000Z (almost 6 years ago)
• Last Synced: 2024-12-24T20:38:16.459Z (20 days ago)
• Language: JavaScript
• Homepage:
• Size: 19.5 KB
• Stars: 8
• Watchers: 3
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: readme.js
  • License: LICENSE

Awesome Lists containing this project

• awesome-callbags - concat

README

        
/**

 * callbag-concat

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

 *

 * Callbag factory that concatenates the data from multiple (2 or more)

 * callbag sources. It starts each source at a time: waits for the previous

 * source to end before starting the next source. Works with both pullable

 * and listenable sources.

 *

 * `npm install callbag-concat`

 *

 * Example:

 *

 *     const fromIter = require('callbag-from-iter');

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

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

 *

 *     const source = concat(fromIter([10,20,30]), fromIter(['a','b']));

 *

 *     iterate(x => console.log(x))(source); // 10

 *                                           // 20

 *                                           // 30

 *                                           // a

 *                                           // b

 */

const UNIQUE = {};

const concat = (...sources) => (start, sink) => {

  if (start !== 0) return;

  const n = sources.length;

  if (n === 0) {

    sink(0, () => {});

    sink(2);

    return;

  }

  let i = 0;

  let sourceTalkback;

  let lastPull = UNIQUE;

  const talkback = (t, d) => {

    if (t === 1) lastPull = d;

    sourceTalkback(t, d);

  };

  (function next() {

    if (i === n) {

      sink(2);

      return;

    }

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

      if (t === 0) {

        sourceTalkback = d;

        if (i === 0) sink(0, talkback);

        else if (lastPull !== UNIQUE) sourceTalkback(1, lastPull);

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

        sink(2, d);

      } else if (t === 2) {

        i++;

        next();

      } else {

        sink(t, d);

      }

    });

  })();

};

export default concat;