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This article is about how to remember JavaScript regular expressions. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

We know that regular expressions are a practical technique for dealing with strings. However, even programmers who are very good at Javascript sometimes forget the syntax of regular expressions, making it a bit tricky to use

1. The three most important symbols in regular expressions:

1.1 B

B has three types of parentheses in regular expressions:

1.1.1 square brackets "[".

Inside the square brackets "[" are the characters to be matched. The content enclosed in brackets matches only a single character.

^ [ab] $

1.1.2 curly braces "{"

Within the curly braces "{" is the specified number of matching characters.

^ [ab] {3} $

1.1.3 parentheses "("

Parentheses "(" are used for grouping.

^ (ab) $

1.2 C

The insert symbol "^" indicates the beginning of the regular expression.

^ a

When used at the beginning of square brackets, it means to exclude the characters in parentheses.

^ [^ 0-9] $

1.3 $

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

Com$

2. Regular expression verification

Recommend a URL to validate regular expressions: https://regexper.com/

2.1 exampl

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

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

The verification results are as follows:

2.2 '│' symbol is equivalent to OR operation

^ (1 | 2) $

3. Shortcut command

3.1\ d represents a number [0-9] Note that d is preceded by an escape character\

^\ d$

Capital D:\ D means non-numeric

^\ D$

3.2 any word character underlined\ w

^\ w $

Uppercase W:\ W for non-words

^\ W$

3.30 or more times *

^ [0-9] * $

3.4 at least one occurrence +

^ [0-9] + $

3.50 times or 1 time?

^ [0-9]? $

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