Created
April 16, 2022 23:56
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wonka (wonka.kitten.sh) , custom operators code
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import { fromArray, fromValue, pipe, toPromise } from "wonka"; | |
function talkbackPlaceholder(a) {} | |
const customTake = (max) => (source) => (sink) => { | |
let taken = []; | |
let talkback = talkbackPlaceholder; | |
let ended = false; | |
return source((signal) => { | |
if (typeof signal === "number") { | |
// stream has ended, handle it | |
fromValue(taken)(sink); | |
} else { | |
if (signal.tag) { | |
// data is available and can be transformed / triggered/ read/ etc | |
if (taken.length < max) { | |
taken.push(signal[0]); | |
talkback(0); | |
if (taken.length === max && !ended) { | |
// we're done with reading, stop here | |
talkback(1); | |
fromValue(taken)(sink); | |
} | |
} | |
} else { | |
console.log("assign talkback"); | |
// talkback is available and should be assigned | |
talkback = signal[0]; | |
} | |
// either way, trigger a next | |
talkback(0); | |
} | |
}); | |
}; | |
function sum(source) { | |
return function (sink) { | |
let total = 0; | |
let talkback = talkbackPlaceholder; | |
return source(function (signal) { | |
if (typeof signal == "number") { | |
fromValue(total)(sink); | |
return; | |
} | |
if (signal.tag) { | |
total += parseInt(signal[0], 10); | |
talkback(0); | |
} else { | |
talkback = signal[0]; | |
} | |
talkback(0); | |
}); | |
}; | |
} | |
async function main() { | |
const result = await pipe(fromArray([1, 2, 3, 4]), sum, toPromise); | |
console.log({ result }); | |
} | |
main(); |
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