javascript style.display not working with buttons

Question

As you can see, I try to make two input buttons (one is shown, the other is hidden) that when clicked, displays the other and hides itself. btn displays a canvas as well as btn2 when clicked but btn2's onclick method doesn't run.

var btn = document.getElementById("btn");
var btn2 = document.getElementById("btn2");
btn2.style.display = "none";

btn.onclick = function () {
    btn.style.display = "none";
    btn2.style.display = "block";
    document.body.innerHTML += '<canvas id="someId"></canvas>';

};

btn2.onclick = function() {
    btn2.style.display = "none";
  btn1.style.display = "block";
    document.getElementById("someId").remove();
};

canvas {
    border: 1px dotted black;
}

<input id='btn' type="submit" value='REMOVE THAT!!!'></input>
<input id="btn2" type="submit" value="return to menu" display="none"></input>

Answer 1

The problem is with this line:

document.body.innerHTML += '<canvas id="someId"></canvas>';

You're appending to the HTML of the body, which is bad practice because it has to re-render all elements and as such, you've lost the click handler for btn2.

The solution is to append the canvas as an element like so:

var canvas = document.createElement('canvas');
canvas.id = 'someId';
document.body.appendChild(canvas);

Now, the browser will append the canvas without destroying and recreating any other elements.

Also, you used btn1 which does not exist, change to btn.

var btn = document.getElementById("btn");
var btn2 = document.getElementById("btn2");
btn2.style.display = "none";

btn.onclick = function () {
    btn.style.display = "none";
	btn2.style.display = "block";
    var canvas = document.createElement('canvas');
    canvas.id = 'someId';
    document.body.appendChild(canvas);

};

btn2.onclick = function() {
	btn2.style.display = "none";
  btn.style.display = "block";
	document.getElementById("someId").remove();
};

canvas {
    border: 1px dotted black;
}

<input id='btn' type="submit" value='REMOVE THAT!!!'></input>
<input id="btn2" type="submit" value="return to menu" display="none"></input>