Adding a Leading Zero in 1 Line in JavaScript

At work, I recently ran into a scenario where we were capturing a user’s date of birth (DOB). This information is collected in 3 fields day, month, and year. If your DOB is January 7, 1962, people were inputting 1 for the month, 7 for the day, and 1962 for the year. This sounds good but our back-end database required both the month and day to be 2 digits. So I needed to find a way to add a leading zero for both…