Number Padding In JavaScript

Padding numbers in JavaScript

// Define new date, result
let d = new Date(), result;
// Set new date
d.setDate(d.getDate() + 20);
// Return result
result = ('0' + d.getDate()).slice(-2) + '/' + ('0' + (d.getMonth()+1)).slice(-2) + '/' + d.getFullYear();

Explanation:
.slice(-2) returns the last 2 characters of the string.

if the d.getMonth() returns 9, .slice(-2) returns ("0" + "9") as "09" which is the last 2 characters.

i.e: ("0" + "9").slice(-2) => "09"

However, if d.getMonth() returns 10, .slice(-2) returns ("0" + "10") as "10".

i.e: ("0" + "10").slice(-2) => "10"