change input field border color javascript code example

Example 1: change input border color when selected

input:focus {
	outline: none;
  	border: 1px solid red;
}

Example 2: how to change input border color with js

document.getElementById("fName").className = document.getElementById("fName").className + " error";  // this adds the error class

document.getElementById("fName").className = document.getElementById("fName").className.replace(" error", ""); // this removes the error class