Regex Examples and Explanation

Regular expressions are a powerful tool for matching patterns in strings. Here are a few common regular expressions that are useful in programming:

1. \d: This matches any digit (0-9).
2. \w: This matches any word character (a-z, A-Z, 0-9, _).
3. \s: This matches any whitespace character (space, tab, newline).
4. .: This matches any character except for a newline.
5. *: This matches zero or more of the preceding character or group.
6. +: This matches one or more of the preceding character or group.
7. ?: This matches zero or one of the preceding character or group.
8. ^: This matches the start of a string.
9. $: This matches the end of a string.
10. {n}: This matches exactly n of the preceding character or group.
11. {n,}: This matches n or more of the preceding character or group.
12. {n,m}: This matches at least n and at most m of the preceding character or group.

Here are a few examples of regular expressions that are commonly used in programming:

1. Validation:

• Email address: /^[a-zA-Z0-9.!#$%&'*+/=?^_{|}~-]+@a-zA-Z0-9?(?:.a-zA-Z0-9?)*$/`
• Phone number: /^(?:(?:\+?1\s*(?:[.-]\s*)?)?(?:\(\s*([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9])\s*\)|([2-9]1[02-9]|[2-9][02-8]1|[2-9][02-8][02-9]))\s*(?:[.-]\s*)?)?([2-9]1[02-9]|[2-9][02-9]1|[2-9][02-9]{2})\s*(?:[.-]\s*)?([0-9]{4})(?:\s*(?:#|x\.?|ext\.?|extension)\s*(\d+))?$/`

2. Parsing:

• Extracting URLs from a piece of text: /https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&\/\/=]*)/`
• Extracting IP addresses: /\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b/`

These are just a few examples, and the specific regular expression that you’ll need will depend on the task you’re trying to accomplish. It’s a good idea to become familiar with the full range of options available to you when working with regular expressions in your programming projects.