Regular expression, also known as regular expression, regular expression, regular expression, regular expression, regular expression (English: Regular Expression, often abbreviated as regex, regexp or RE in code).

Regular expressions use a single string to describe and match a series of strings that match a certain syntax rule. In many text editors, regular expressions are often used to retrieve and replace text that matches a certain pattern.

1. Character class

1. Character class: can match any character it contains

eg: /[abc]/ matches any one of the letters "a", "b", and "c"

2. Negative character class: Define the negative character class through the "^" character, which matches all characters not contained in square brackets. When defining a negative character class, put a "^" symbol as the first character inside the left bracket.

? eg:/[^abc]/ matches all characters except "a", "b", and "c".

3. \s: matches spaces, tabs and other Unicode whitespace characters;

. : Any character except newlines and other Unicode line terminators.