Some of the things I've noticed:

• Avoid global variables
• It's a good decision to avoid var keyword as the variable declaration in 2020. Read about let and const
• Some of the variables could be more descriptive
• Use classes instead of html tags for styling
• Instead of styling in JS. Add a CSS class in JS instead
• Look how packed with logic Your for loop is. It's a bit hard to understand + avoid complicated logic inside of loops. Performance is important

Some of the things I've noticed:

• Avoid global variables
• It's a good decision to avoid var keyword as the variable declaration in 2020. Read about let and const
• Some of the variables could be more descriptive
• Use classes instead of html tags for styling
• Instead of styling in JS. Add a CSS class in JS instead
• Look how packed with logic Your for loop is. It's a bit hard to understand + avoid complicated logic inside of loops. Performance is important
• It's not a good practice to separate the dom elements using <br>