fp on async generators.js

async function* seconds() {
    let i = 0
    while (i < 10) {
        await new Promise(resolve => setTimeout(resolve, 1000))
        i++
        yield i
    }
}

function map(f, gen) {
    return async function* () {
        for await (let value of gen) {
            yield f(value)
        }
    }
}

function filter(f, gen) {
    return async function* () {
        for await (let value of gen) {
            if (f(value)) { yield value }
        }
    }
}

function fold(f, seed, gen) {
    return async function* () {
        let acc = seed
        for await (let value of gen) {
            acc = f(value, acc)
            yield acc
        }
    }
}

const tens = map(seconds(), n => n * 10)

const main = async () => {
    for await (let x of tens()) {
        console.log(x)
    }
}