Regular expression rules

^ is the delimiter that represents the beginning of the matching string;
[+-], the brackets indicate that the contents are matched to the requirements, so this means "+" or "-";
\D,[0-9] abbreviated form, that is, matching numbers;
$ is also the delimiter that represents the end of the matching string;

See the question mark (?) after you know the above. and asterisk (*): Following a pattern content is a quantifier, used to limit the number of pattern content matching, for example, I want to match a minimum of 1, a maximum of 3 numbers, such as 4, 20, 123, 226 such as, previously explained that a single number can be expressed in [0-9] or \d, So how do you mean a minimum of 1 matches, up to 3 times? Very simple, just after the pattern with curly braces to denote quantifiers, in the form of {lower bound, upper limit}, that is the case [0-9]{1,3} or \d{1,3}. Similarly, [0-9]{2} means that only 2 digits can be matched (one less than the other), [0-9]{2,} indicates at least 2 digits (note the comma within the curly braces), and [0-9]{,2} represents a maximum of 2 digits (note the comma of the curly braces).
For frequently used quantifiers
There is also a shorthand in the regular, {0,1} shorthand is a question mark (either no or only once)
{0,} shorthand is an asterisk (any number or unlimited)
{1,} shorthand is a plus sign (at least once)

. * denotes any number of arbitrary characters for example: A.*b, which will match the longest string starting with a and ending with B. If you use it to search for Aabab, it will match the entire string aabab. This is called a greedy match.
Sometimes we need more lazy matching, which is to match as few characters as possible. The qualifier given above can be converted to lazy matching mode, just add a question mark after it. So. * is meant to match any number of repetitions, but with minimal repetition in the premise that the entire match succeeds
A.*?b matches the shortest, starting with a string ending with B. If you apply it to Aabab, it will match AaB (first to third character) and AB (fourth to fifth characters)
The *, +, and? Qualifiers are greedy because they match as many words as possible, but only after they are added with one? You can implement a non-greedy or minimal match.

^ matches the starting position of the input string, unless used in a square bracket expression, which indicates that the character set is not accepted
() to mark the start and end of a sub-expression

\CX matches the control character indicated by X. For example, \cm matches a control-m or carriage return. The value of x must be one of a-Z or a-Z. Otherwise, c is treated as a literal ' C ' character.
\f matches a page break. Equivalent to \x0c and \CL.
\ n matches a line break. Equivalent to \x0a and \CJ.
\ r matches a carriage return character. Equivalent to \x0d and \cm.
\s matches any whitespace character, including spaces, tabs, page breaks, and so on. equivalent to [\f\n\r\t\v].
\s matches any non-whitespace character. equivalent to [^ \f\n\r\t\v].
\ t matches a tab character. Equivalent to \x09 and \ci.
\v matches a vertical tab. Equivalent to \x0b and \ck.

Regular expression rules