xstream-tuplewise/index.js

An xstream operator that groups consecutive events into N-tuples

import { Stream } from 'xstream';

class TuplewiseOperator {
    constructor(n, ins) {
        this.n = n;
        this.ins = ins;
        this.type = 'tuplewise';
        this.buf = [];
        this.out = null;
    }
    _start(out) {
        this.out = out;
        this.ins._add(this);
    }
    _stop() {
        this.ins._remove(this);
        this.out = null;
        this.buf = [];
    }
    _n(t) {
        const u = this.out;
        if (!u)
            return;
        this.buf.push(t);
        if (this.buf.length >= this.n) {
            u._n(this.buf);
            this.buf = this.buf.slice(1, this.n);
        }
    }
    _e(err) {
        const u = this.out;
        if (!u)
            return;
        u._e(err);
    }
    _c() {
        const u = this.out;
        if (!u)
            return;
        u._c();
    }
}
function tuplewise(n) {
    return function ($) {
        if (n === 0) {
            return $.map((_) => []).startWith([]);
        }
        return new Stream(new TuplewiseOperator(n, $));
    };
}

export { tuplewise };