how to get the border width of an element js code example

Example 1: border width css

.element {
  border-width: 2px;
}

Example 2: border width css

#some-div {
  /* [WIDTH] [FILL MODE] [COLOR] */
  border: 5px solid #f00; 
  
  /* draws solid a red line of 5px
  between the padding (inside the div)
  and the margin (outside the div) */
}