JavaScript Regular expression popular explanation fast memory

1. The most important three symbols in regular expressions:

1.1 B

In regular expressions, B has 3 types of parentheses:

1.1.1 square brackets "[".

The square brackets "[" are the characters that need to be matched. Bracketed content only matches one single character.

^[ab]$

1.1.2 Curly Brace "{"

The curly brace "{" is the number of matching characters specified.

^[ab]{3}$

1.1.3 Parenthesis "("

The parentheses "(" are used for grouping.)

^ (AB) $

1.2 C

The caret "^" indicates the beginning of the regular type.

^a

^ When used at the beginning of the brackets, the characters in parentheses are excluded.

^[^0-9]$

1.3 $

The dollar sign "$" indicates the end of the regular type.

com$

2. Regular expression validation

Recommend a validation regular expression URL: https://regexper.com/

2.1 Example

^[0-9]{3,7}$

The above regular expression is a number with a minimum length of 3 and a maximum of 7.

The result of the validation is:

2.2 ' │ ' symbol equals or operation

^ (1|2) $

3. Quick command

3.1 \d = number [0-9] Note D preceded by an escape character \

^\d$

Uppercase d:\d denotes non-numeric

^\d$

3.2 Underline any word character \w

^\w$

Capital W: \w denotes non-word

^\w$

3.3 0 times or more occurrences *

^[0-9]*$

3.4 At least once occurred +

^[0-9]+$

3.5 0 or 1 times?

^[0-9]?$

2017.8.25 Update

4. Non-greedy mode

Add a question mark directly behind the quantifier? It's a non-greedy pattern.

/(
JavaScript Regular expression popular explanation fast memory