How to use Regular Expressions for custom input validation
A regular expression - or REGEX - is a sequence of characters that specifies a match pattern in text.In MIDAS, Regular Expressions can be used to validate entries into custom input fields.
For instance, you could use a Regular Expression to ensure that an input is of a certain length, only contains certain characters, or matches a specific format.
Regular expressions can be very powerful and versatile tools. However, they can also be difficult to learn and use.
Simple Regular Expression Examples
| Description | REGEX | Example That Matches | Example That Doesn't Match |
| Match any value | . | MIDAS | |
| Value must start with the letters "BOOK" | ^BOOK | BOOKED | BLUEBOOK |
| Value must end with the letters "ING" | ING$ | BOOKING | BOOKED |
| Value must contain "BOOKING" | BOOKING | YOUR BOOKING DETAILS | YOU BOOKED |
| Value must be exactly "BOOKING" | ^BOOKING$ | BOOKING | YOUR BOOKING |
| Value must contain a number (digit) | \d | 2 BOOKINGS | TWO BOOKINGS |
| Value must not contain a number (digit) | \D | TWO BOOKINGS | 2 BOOKINGS |
| Value must be exactly "BOOK", followed by two single digit numbers | ^BOOK\d\d$ | BOOK43 | BOOKING43 |
| Value must start with "BOOK", followed by a three single digit number | ^BOOK\d{3} | BOOK432 | BOOK43 |
| Value must contain "BOOK", followed by either a number 1, 2, or 3 | BOOK[1-3] | BOOK2 | BOOK4 |
| Value must start with any uppercase letter | ^[A-Z] | Abc123 | abc123 |
| Value must end with any lowercase letter | [a-z]$ | 123abc | abc123 |
| Value must be at least 5 characters in length | .{5} | BOOKING | BOOK |
| Value must be exactly 4 characters in length | ^.{4}$ | BOOK | BOOKING |
| Match a number in the format ###-###-#### | \d{3}-\d{3}-\d{4} | 123-456-7890 | 123-4567-890 |
Explanation
Here's an explanation of some of the REGEX characters you'll have noticed in the above examples:| Expressions | Meaning |
| ^ | Matches at the start of a value |
| $ | Matches at the end of a value |
| . | Matches any character |
| \d | Matches any single number (digit) |
| \D | Matches any single character that's not a number (digit) |
| {3} | Matches the preceding expression three times |
| [A-Z] | Matches any uppercase letter between A and Z |
| [a-z] | Matches any lowercase letter between A and Z |
| [A-Za-z] | Matches any letter between A and Z, regardless of case |
| [1-3] | A number in the range 1 - 3 |
← Return to the Knowledge Base