Answer 1

what i have seen from your codes.

you have forgotten to add semicolon (;) after every statement

ie.
var elem = document:getElementById(“example”);
elem.style.borderWidth = “10px”;
elem.style.borderColor = “#FFF”;

Answer 2

@Norberttony share your complete code 😅.

Answer 3

or just do elem.style.border="5px solid black";
kill two birds with a stone