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callbag-combine
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callbag-combine

👜 Callbag factory that combines data from multiple callbag sources

by André Staltz

1.2.0 (see all)License:MITTypeScript:DefinitelyTyped
npm i callbag-combine
Readme

/**

  • callbag-combine

  • Callbag factory that combines the latest data points from multiple (2 or
  • more) callbag sources. It delivers those latest values as an array. Works
  • with both pullable and listenable sources.
  • npm install callbag-combine
  • Example:
  • const interval = require('callbag-interval');
    
  • const observe = require('callbag-observe');
    
  • const combine = require('callbag-combine');
    
  • const source = combine(interval(100), interval(350));
    
  • observe(x => console.log(x))(source); // [2,0]
    
  •                                       // [3,0]
    
  •                                       // [4,0]
    
  •                                       // [5,0]
    
  •                                       // [6,0]
    
  •                                       // [6,1]
    
  •                                       // [7,1]
    
  •                                       // [8,1]
    
  •                                       // ...
    
    */

const EMPTY = {};

const combine = (...sources) => (start, sink) => { if (start !== 0) return; const n = sources.length; if (n === 0) { sink(0, () => {}); sink(1, []); sink(2); return; } let Ns = n; // start counter let Nd = n; // data counter let Ne = n; // end counter const vals = new Array(n); const sourceTalkbacks = new Array(n); const talkback = (t, d) => { if (t === 0) return; for (let i = 0; i < n; i++) sourceTalkbacks[i](t, d); }; sources.forEach((source, i) => { vals[i] = EMPTY; source(0, (t, d) => { if (t === 0) { sourceTalkbacks[i] = d; if (--Ns === 0) sink(0, talkback); } else if (t === 1) { const _Nd = !Nd ? 0 : vals[i] === EMPTY ? --Nd : Nd; vals[i] = d; if (_Nd === 0) { const arr = new Array(n); for (let j = 0; j < n; ++j) arr[j] = vals[j]; sink(1, arr); } } else if (t === 2) { if (--Ne === 0) sink(2); } else { sink(t, d); } }); }); };

module.exports = combine;

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VersionTagPublished
1.2.0
latest
4yrs ago
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