JavaScript：用于创建图片副本的循环不起作用

I'm making a platformer in JavaScript and HTML, and I've run into a problem. Some code that is supposed to duplicate and print an image of a box (the floor that the character walks on) isn't working, and is thus just displaying a white screen when I run it. I have checked the console of my browser, but it says there are no errors. Here's the HTML file:I'm making a platformer in JavaScript and HTML,