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RegEx: Basic Introduction
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In this guide, I'll introduce you to RegEx.
RegEx stands for 'Regular Expression'. It is used to make search patterns.
What a RegEx filter is made of
This is an example of a very basic RegEx filter, it will select every occurrence of 'word' in the target string:
/word/gIt consists of two delimiters, in this case we use slashes ('/'), the content (the filter pattern) between them, which is what we filter by and the flags after the delimiters, which configure the filter.
RegEx Tokens
RegEx Tokens can be utilized in the filter pattern.
Following Tokens, but not limited by, are available (at least in JavaScript). Here's a collection with examples and explanations:
- . Any single character.
- a|b|c Either a, b or c.
- [abc] Any single character mentioned inside square brackets.
- [a-z] Any single character between a and z.
- [^abc] Any single character, except ones mentioned inside square brackets.
- [^a-z] Any single character, except between a and z.
- a? Zero or one of a.
- a* Zero or more of a.
- a+ One or more of a.
- a{2} Two of a.
- a{2,} Two or more of a.
- a{2,4} Between 2 and 4 of a.
- (abc) Capture group.
- (?=abc) Positive lookahead.
- (?!abc) Negative lookahead.
- (?<=abc) Positive lookbehind.
- (?<!abc) Negative lookbehind.
RegEx Flags
Like mentioned before, flags can configure how your filter works. The following flags are available (at least in JavaScript):
- g Global - Don't return after first match.
- m Multi line - ^ and $ match start and end of a line.
- i Insensitive - Case insensitive filter.
- y Sticky - Anchor to start of filter pattern or at end of most recent match.
- u Unicode - Utilize full Unicode.
- s Singe line - Dot token specifically also counts newline as character.