Text Processing with JavaScript

Recipe 29

Repeating Part of a Regex with Quantifiers

Task

Suppose you want to add an option to your program that allows users to log in with a PIN code. The main benefit of using a PIN instead of a password is faster login. I tend to put my computer to sleep when I’m away, even for a short time. Conveniently, my OS lets me log in quickly with only a PIN code.

Say you want to implement a similar feature for your application. You need to write a regex pattern that 1) validates the input is digits and 2) ensures the number of digits is between 4 and 6 characters.

Solution

Place a pair of curly brackets after the \d character class to specify how many times the digits should occur:

part_2/quantifiers/quantifiers_ex1.js

const re = /^\d{4,6} ...