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

👜 Callbag operator that conditionally lets data pass through
https://github.com/staltz/callbag-filter

Last synced: about 2 months ago
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👜 Callbag operator that conditionally lets data pass through

• Host: GitHub
• URL: https://github.com/staltz/callbag-filter
• Owner: staltz
• License: mit
• Created: 2018-01-29T10:49:08.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2019-02-09T11:04:38.000Z (over 5 years ago)
• Last Synced: 2024-07-25T14:24:00.477Z (about 2 months ago)
• Language: JavaScript
• Homepage:
• Size: 8.79 KB
• Stars: 6
• Watchers: 3
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: readme.js
  • License: LICENSE

Awesome Lists containing this project

• awesome-callbags - filter

README

        
/**

 * callbag-filter

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

 *

 * Callbag operator that conditionally lets data pass through. Works on either

 * pullable or listenable sources.

 *

 * `npm install callbag-filter`

 *

 * Example:

 *

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

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

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

 *

 *     const source = filter(x => x % 2)(fromIter([1,2,3,4,5]));

 *

 *     iterate(x => console.log(x))(source); // 1

 *                                           // 3

 *                                           // 5

 */

const filter = condition => source => (start, sink) => {

  if (start !== 0) return;

  let talkback;

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

    if (t === 0) {

      talkback = d;

      sink(t, d);

    } else if (t === 1) {

      if (condition(d)) sink(t, d);

      else talkback(1);

    }

    else sink(t, d);

  });

};

module.exports = filter;