fix: 2-ui/1-document/09.../4.../solution.view

Author: leviding

2-ui/1-document/09-size-and-scroll/4-put-ball-in-center/solution.view/index.html

@@ -29,8 +29,10 @@
     let ball = document.getElementById('ball')
     let field = document.getElementById('field')
 
-    ball.style.left = Math.round(field.clientWidth / 2 - ball.offsetWidth / 2) + 'px'
-    ball.style.top = Math.round(field.clientHeight / 2 - ball.offsetHeight / 2) + 'px'
+    window.onload = function() {
+      ball.style.left = Math.round(field.clientWidth / 2 - ball.offsetWidth / 2) + 'px';
+      ball.style.top = Math.round(field.clientHeight / 2 - ball.offsetHeight / 2) + 'px';
+    };
   </script>