# Regular Expressions

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You can find the full description of RegExp in [Wikipedia](https://en.wikipedia.org/wiki/Regular_expression). This article will provide you with a short cheat sheet of frequently used expressions.
{% endhint %}

{% hint style="warning" %}
**No JS evaluation** is needed in regex! Just remember to use **'\*'** after the expression.
{% endhint %}

### `rexExp` cheat sheet

| Meta-character | Description                                                        |
| -------------- | ------------------------------------------------------------------ |
| `.`            | Matches any character                                              |
| `+`            | Matches the preceding pattern element one or more times.           |
| `?`            | Matches the preceding pattern element zero or one time.            |
| `\|`           | Separates alternate possibilities, `A\|B = A or B`                 |
| `^`            | Matches the beginning of a line or string.                         |
| `$`            | Matches the end of a line or string.                               |
| `[ ]`          | Denotes a set of possible character matches. `[ABC] = A or B or C` |
| `\`            | Escapes special characters                                         |

### Frequently used Regular Expressions

| Case                          | regExp (you can copy-paste them right into Directual)                                                   |
| ----------------------------- | ------------------------------------------------------------------------------------------------------- |
| Check email format            | `.+@.+\..*`                                                                                             |
| Check particular email domain | `.+@yourdomain\.com*`                                                                                   |
| Any digit number              | `[0-9]*`                                                                                                |
| Any latin character           | `[a-zA-Z]*`                                                                                             |
| Greetings                     | `.*hello\|hi\|good morning\|good evening\|salut.*`                                                      |
| URL                           | `https?:\/\/(www.)?[-a-zA-Z0-9@:%.`*`+~#=]{1,256}.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%`*`+.~#?&//=]*)` |

Useful service for composing a regular expression: [regex101.com](https://regex101.com/)


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