document.addEventListener("DOMContentLoaded", ()=>{
document.getElementById("someid").addEventListener("click", () => {
alert("Hello");
}, false);
});

function dblSize() {
	var pelem = document.getElementsByTagName('p');
	if (pelem.length == 0) {
	} else {
		for (let i of pelem) {
			i.style.fontSize = '200%';
		}
	}
}
window.addEventListener("load", function() {
	document.body.addEventListener("click", dblSize);
});