A koa server that always responds with the next number in a fibonacci sequence and stops after the 100th number.

fib-server.js

import 'babel-polyfill'
import Koa from 'koa'
const app = new Koa();

function* fibonacci () {
    let [a, b] = [0, 1]
    while (true) {
        [a, b] = [b, a + b]
        yield a
    }
}

function* take(n, iterator) {
    for (let item of iterator) {
        if (n-- === 0) break
        yield item
    }
}

const seq = take(100, fibonacci())

app.use(async (ctx, next) => {
    var start = new Date;
    await next();
    var ms = new Date - start;
    console.log('%s %s - %sms', ctx.method, ctx.url, ms);
})


app.use(async ctx => {
    ctx.body = seq.next().value
});

app.listen(1337)