Regular Expressions

For text operation rules you can also use regular expressions. We mostly use regular expressions (Regex) for input-validation.

You can find online many Regex tutorials and ALWAYS check your Regex online. E.g. here: Regexpal.com

A very good Regex Cheat Sheet: https://cheatography.com/davechild/cheat-sheets/regular-expressions/

Here are some examples:

• a|b|c|d
• 1|2|3|4|5
• [0-9]+
• [a-zA-Z]*
• [a-z]{2,4}
• \d+