CSS:

@keyframes amplifying-div {
    0% {
        width: 5%;
        height: 5%;
    }
    100% {
        width: 90%;
        height: 90%;
    }
}

.play-amplifying{
    animation-name: amplifying-div;
    animation-duration: 4s;
    animation-fill-mode: forwards;
}

JS:
let div=document.querySelector("#imageDiv");
div.classList.remove("play-amplifying");
div.style.display="block";
div.classList.add("play-amplifying");