ES6 generators test

wave.js

"use strict";

(function() {

    function* map(iterable, fn) {
        for (let item of iterable) {
            yield fn(item);
        }
    }

    function* cycle(generator) {
        let iter = generator();

        while (true) {
            let item = iter.next();

            if (item.done) {
                iter = generator();
                continue;
            }

            yield item.value;
        }
    }

    function* waveFn(config) {
        let x = 0;
        while (true) {
            x++;
            let B = (2 * Math.PI) / config.period;
            let A = config.amplitude * Math.cos((B * x) / config.variation);
            let D = config.vShift;
            let y = A * Math.sin(B * x) + D;
            yield Math.round(y);
        }
    }

    function* numRange(start, end) {
        for (let n = start; n < end; n++) {
            yield n;
        }
    }

    function* abcRange() {
        function abcGenerator() {
            let chr = n => String.fromCharCode((n % 26) + 65);
            return map(numRange(0, 26), chr);
        }

        yield* cycle(abcGenerator);
    }

    function* zip(a, b) {
        while (true) {
            let aValue = a.next(),
                bValue = b.next();

            if (aValue.done || bValue.done) {
                return;
            }

            yield [aValue.value, bValue.value];
        }
    }

    function scheduleNext(iterable, ms) {
        let advance = iterable => iterable && iterable.next();
        setInterval(advance, ms, iterable);
    }

    function generateWave() {

        function printWave(f_C) {
            let n = f_C[0],
                c = f_C[1],
                space = 100;

            if (n < 0) {
                space -= Math.abs(n);
            }

            process.stdout.write(' '.repeat(space));
            console.log(c.repeat(Math.abs(n)));
        }

        let sine = waveFn({amplitude: 75, variation: 1.5, period: 50, vShift: 0}),
            letters = abcRange(),
            wave = zip(sine, letters),
            pausedWave = scheduleNext(map(wave, printWave), 50);

        scheduleNext();
    }

    generateWave();

})();