Make spritesheet of bunch of images

spritesheet.html

<canvas width="4096" height="3072" id=canvas></canvas>
<script>
let ctx = canvas.getContext`2d`;
window.onload = async () => {
	let grid = 12;
	canvas.width = grid*260; // grid * tile width
	canvas.height = grid*220; // grid * tile height
	for(let i=0;i<grid*grid;i++) {
		let image = await loadImage(`render_${(""+i).padStart(5,"0")}.png`);
		let idx = i%grid, idy = i/grid|0;
		ctx.drawImage(image, idx*image.width, idy*image.height);
	}
}
function loadImage(src) {
	return new Promise((resolve, reject) => {
		let img = new Image();
		img.onload = () => resolve(img);
		img.onerror = reject;
		img.src = src;
	});
}
</script>