Regular Expressions Syntax
Explore JavaScript regular expression syntax to understand how to create patterns for matching strings. Learn about brackets for character ranges, quantifiers for frequency, lookaround assertions, character literals, and metacharacters. This lesson helps you grasp the essentials of RegEx syntax to apply in pattern matching and string validation tasks.
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We know that regular expressions are used for pattern matching. Let’s look at how to write and understand a RegEx.
Syntax
A regular expression can find a matching substring or test if a string passes a certain criterion. Let’s look at the syntax of RegEx.
Brackets
Brackets, or square brackets [], are patterns that find a range of characters in the string. The brackets encapsulate the criteria or pattern that the string needs to satisfy. This chart shows how brackets are used.
| Expression | Description |
|---|---|
[...] |
Any of the characters encapsulated in the brackets with ... representing any character or pattern. |
[^...] |
Not any character encapsulated in the brackets where ... represents any character or pattern. The ^ represents Not. |
[0-9] |
Any number between 0 and 9 |
[a-z] |
Any character from lowercase letter ‘a’ to lowercase letter ‘z’ |