How to add characters to the beginning or end of a string if it's less than a certain length with vanilla JS
Today, we’re going to look at two JavaScript methods you can use to add characters to the beginning and end of a string when it’s less than a certain length.
Let’s dig in!
String.padStart()
You can use the String.padStart() method to add characters to the beginning of a string if it’s less than a certain length. This is particularly useful for numbers that need leading 0’s (but can do so much more than that).
The String.padStart() method accepts two arguments: the length the string should be, and what characters to add if it’s not that length. The characters to use is option, and defaults to a space ().
// Add a leading zero for hours below 10
let hour3 = '3';
let hour12 = '12';
// returns "03"
hour3.padStart(2, '0');
// returns "12"
hour12.padStart(2, '0');
String.padEnd()
You can use the String.padEnd() method to add characters to the end of a string if it’s less than a certain length. This is particularly useful for numbers that need trailing 0’s (but can do so much more than that).
The String.padEnd() method accepts two arguments: the length the string should be, and what characters to add if it’s not that length. The characters to use is option, and defaults to a space ().
// Add a leading zero for hours below 10
let minutes0 = '0';
let minutes12 = '12';
// returns "00"
minutes0.padEnd(2, '0');
// returns "12"
minutes12.padEnd(2, '0');