Some promises

promises.js

function tickingPromise(seconds, value) {
    return new Promise((resolve, reject) => {
        let i = 0;
        let timer = setInterval(() => {
            i += 1
            console.log("Tick", i)
            if (i == seconds) {
                resolve(value)
                clearInterval(timer)
            }
        }, 500)
    })
}

function impatientWaiter(seconds, value) {
    console.log(`Resolving with ${value} in ${seconds}`)
    return new Promise((resolve, reject) => {
        if (seconds < 10) {
            setTimeout(() => { resolve(value) }, seconds * 500)
        } else {
            reject(Error(`${seconds} seconds is _way_ too long`))
        }
    })
}

function probably(value, failureOnceIn=4) {
    return new Promise((resolve, reject) => {
        if (Math.random() > 1/failureOnceIn) {
            const wait = 500 * (Math.random() + 0.5)
            setTimeout(() => { resolve(value) }, wait)
        } else {
            reject(Error("Random failure"))
        }
    })
}

let keyListenerQueue = []

document.addEventListener("keypress", (event) => {
    console.log("you pressed", event.which)

    let fn
    if (fn = keyListenerQueue.shift()) {
        fn(event.which)
    }
})

function getKeyPress() {
    return new Promise((resolve, reject) => {
        keyListenerQueue.push(resolve)
    })
}