Plz help fix the bug

Question

https://code.sololearn.com/WaM5kDMNTHyj/?ref=app

Answer 1

The problem is that u are change the canvas width/height on every loop inside setInterval(). This causes it to clear it everytime, effectively allowing only one rect to be shown since the other gets cleared.
Move ur canvas/ctx initialization to the onload() so u only do this once.
Also i would suggest to use requestAnimationFrame() instead of setInterval() for animating things

Answer 2

Giorgos Dim can I have example code

Answer 3

https://code.sololearn.com/WUFXZte5k2Qw/?ref=app