How do I add a preloader when my setTimeout is in NodeJS, below is the code to call the api and set a delay for 10s:

function delay(s){
    return new Promise(resolve => setTimeout(resolve,s));
}


async function getXml(){
let ans;
await delay(10000)
const {data} = await axios.get('https://gist.githubusercontent.com/SwayamShah97/a3619c5828ac8ed8085c4ae295a855d9/raw/e4e372552e042bd8bd9e8ab87da93eb030114f86/people.xml');
xml2js.parseString(data, (err, result) => {
    if(err) {
        throw err;
    }
    ans = result
    
});

I have tried to add the loader using frontend js like this:

window.addEventListener("load", function () {
    const loader = document.querySelector(".loader");
    loader.className += " hidden"; // class "loader hidden"
});

HTML:

<div class="loader">
    <img src="/public/images/coffee-loading.gif" alt="Loading..." />
</div>

CSS:

.loader.hidden {
    animation: fadeOut 10s;
    animation-fill-mode: forwards;
}

@keyframes fadeOut {
    100% {
        opacity: 0;
        visibility: hidden;
    }
} 

How it works is, it waits 10s as it should due to the setTimeout, and then shows the preloader for additional 10s instead of aligning with the delay.

How can I achieve this functionality?