let cache = {};
async function getData(url){
    let result = "";
    if(cache[url] !== undefined) return cache[url].value;

    await fetch(url)
    .then(response => response.json())
    .then(json => cache[url] = {time: new Date(), value: json});

    return cache[url].value;
}

// Interval to clear cache;
setInterval(function (){
    if(Object.keys(cache).length > 0){
        let currentTime = new Date();
        Object.keys(cache).forEach(key => {
            let seconds = currentTime - cache[key].time;

            if(seconds > 10000){
                delete cache[key];
                console.log(`${key}'s cache deleted`)
            }
        })
    }
}, 3000);

getData("https://jsonplaceholder.typicode.com/todos/1")
.then(data => console.log(data));