add some fix

javascript/hw.js

@@ -300,7 +300,7 @@ document.getElementById('undo').onclick = function () {
 	Drawable.drawAll();
 };
 
-color.onchange = () => {
+document.getElementById('color').onchange = () => {
 	selection.forEach((c) => (c.color = color.value));
 	Drawable.drawAll(selection);
 };