Factor out some html helpers

lib/html.ts

@@ -0,0 +1,22 @@
+export function h<Name extends keyof HTMLElementTagNameMap>(
+  name: Name,
+  props: Partial<HTMLElementTagNameMap[Name]>,
+  ...children: Node[]
+): HTMLElementTagNameMap[Name] {
+  const element = Object.assign(document.createElement(name), props);
+  element.append(...children);
+  return element;
+}
+
+export function canvas2d(
+  props: Partial<HTMLCanvasElement>
+): [HTMLCanvasElement, CanvasRenderingContext2D] {
+  const canvas = h("canvas", props);
+
+  const cx = canvas.getContext("2d");
+  if (!cx) {
+    throw new Error("2D rendering context not supported");
+  }
+
+  return [canvas, cx];
+}