Regular Expressions Notes

Modifier (g, i, m)

1. g: full match (without the first match to the stop)

2. i: Ignore case (default case-sensitive)

3. m: multiline search

“He is a boy,Is he?”.replace('/\bis\b/gi','0')
=>  "He 0 a boy,0 he?"

Metacharacters (*,, [], (), {}, +,, $, ^, |.? ,,)

1. [] Character class, one can meet

 [abc] 字符类，（表或，有其中一个即可(a,b,c)）
 [^abc] 字符类取反，none of  (a,b,c) 不包含组合里任意一个
 [a-z] 从a至z的任意字符
 [0-9] 从0至9的任意数字
 [a-zA-Z] 从a至z或A至Z的任意字符

2. All symbols except the carriage return and linefeed
3. \ D numeric characters ([0-9])
4. \ D non-numeric characters ([^ 0-9])
5. \ S whitespace
6. \ S non-whitespace
7. \ W word character (alphanumeric underscore [a-zA-Z_0-9])
8. \ W non-word character
9. {4} quantifier, expressed 4
10. () Grouping
11. Represents one or more + (\ + D 1 represents one or more numbers)
12. ? Represents 0 or 1 (\ d? Represents 0 or a number)

2020-05-06 替换为05-06-2020
var reg = /^(\d{4})[/-](\d{2})[/-](\d{2})$/g
"2020-05-06".replace(reg,'$2-$3-$1')

Boundary (^, $, \ b, \ B)

1. ^ XXX to start (pre-write)
2. $ XXX to the end (after writing)
3. \ b word boundary
4. \ B non-word boundary