How to write inside a DIV box with javascript

I'm making a mini-game where a player attacks a npc and in the center is a white box (div) that I call (log), because when the player damages/attacks the npc, I want to be able for that open white space to log what happened.

I'm using the getElementById(log) and then adding something along the lines of "document.write("You attacked X npc"), but its not working.

Any idea on how I can get text INSIDE the box and not outside it? Thanks

document.getElementById('log').innerHTML += '<br>Some new content!';

<div id="log">initial content</div>

You can use one of the following methods:

document.getElementById('log').innerHTML = "text";

document.getElementById('log').innerText = "text";

document.getElementById('log').textContent = "text";

For Jquery:

$("#log").text("text");

$("#log").html("text");