Understanding regular expressions in JS

1. What are regular expressions? Regular expressions: rules, which allow computers to understand the rules we write. In essence, regular expressions are a set of regular strings. a

2 How to learn Regular expression

\d represents numbers
\D represents non-digits
\s represents spaces

1） 用这些特定的字符去写一套规则(我想要的规则，我想要一套邮箱的规则、qq号的规则、电话号码的规则等等)
2） 使用的时候，拿需要判断的内容放到这套规则里面去检测

3 Some methods related to regular expressions in js
Test
Repalce
match
Search
4 Matching sub-item (sub-pattern) – ()
5 Character class – []
1 contains the relationship of or
2 Can write range [0-9][a-z][A-Z]
3. Use ^ inside [] to indicate non. Note: Use ^ outside [] to indicate the beginning
6 Escape characters
. represents any character in the regular expression, and . is converted into a real character.
\b \B
\s \S
\d \D
\w \W
\1 Repeat the first sub-item \2 \3 …
7 Quantifier Modifies the quantity
{4, 7} Greater than or equal to 4 Less than or equal to 7
{4, } greater than or equal to 4
{4} is equal to 4
? 0 times or 1 time
* Greater than or equal to 0
+ Greater than or equal to 1

1 What is a regular expression

Regular: Rules, so that the computer can understand the rules we write

Essentially speaking, a regular expression is a String of group rules, a

2 How to learn regular expressions

\d represents numbers
\D represents non-digits
\s represents spaces

1） 用这些特定的字符去写一套规则(我想要的规则，我想要一套邮箱的规则、qq号的规则、电话号码的规则等等)
2） 使用的时候，拿需要判断的内容放到这套规则里面去检测

3 Some methods related to regular expressions in js
Test
Repalce
match
Search
4 Matching sub-item (sub-pattern) – ()
5 Character class – []
1 contains the relationship of or
2 Can write range [0-9][a-z][A-Z]
3. Use ^ inside [] to indicate non. Note: Use ^ outside [] to indicate the beginning
6 Escape characters
. represents any character in the regular expression, and . is converted into a real character.
\b \B
\s \S
\d \D
\w \W
\1 Repeat the first sub-item \2 \3 …
7 Quantifier Modifies the quantity
{4, 7} Greater than or equal to 4 Less than or equal to 7
{4, } greater than or equal to 4
{4} is equal to 4
? 0 times or 1 time
* Greater than or equal to 0
+ Greater than or equal to 1

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