how to change only yhe first letter of a string jvascript code example

Example 1: javascript capitalize first letter

const lower = 'this is an entirely lowercase string';
const upper = lower.charAt(0).toUpperCase() + lower.substring(1);

Example 2: capitalize first carater js

String.prototype.capitalize = function() {
  return this.charAt(0).toUpperCase() + this.slice(1)
}