正则表达式

JavaScript正则表达式详解与实战

Symbols

符号	描述
.	(period) Matches any single character, except for line breaks.
`*`	Matches the preceding expression 0 or more times.
+	Matches the preceding expression 1 or more times.
?	Preceding expression is optional (Matches 0 or 1 times).
^	Matches the beginning of the string.
`$`	Matches the end of the string.

Character groups

符号	描述
\d	Matches any single digit character.
\w	Matches any word character (alphanumeric & underscore).
[XYZ]	Character Set: Matches any single character from the character within the brackets. You can also do a range such as [A-Z]
[XYZ]+	Matches one or more of any of the characters in the set.
[^a-z]	Inside a character set, the ^ is used for negation. In this example, match anything that is NOT an uppercase letter.

Flags: There are five optional flags. They can be used separately or together and are placed after the closing slash. Example: /[A-Z]/g I’ll only be introducing 2 here.

符号	描述
g	Global search
i	case insensitive search

Advanced

符号	描述
(x)	Capturing Parenthesis: Matches x and remembers it so we can use it later.
(?:x)	Non-capturing Parenthesis: Matches x and does not remembers it.
x(?=y)	Lookahead: Matches x only if it is followed by y.

匹配模式

全局模式

严格模式

Sticky模式常用于语句令牌化这种需要严格指定匹配位置的地方：

function tokenize(TOKEN_REGEX, str) {
  let result = [];
  let match;
  while ((match = TOKEN_REGEX.exec(str))) {
    result.push(match[1]);
  }
  return result;
}

const TOKEN_GY = /\s*(\+|[0-9]+)\s*/gy;
const TOKEN_G = /\s*(\+|[0-9]+)\s*/g;

> tokenize(TOKEN_GY, '3 + 4')
[ '3', '+', '4' ]
> tokenize(TOKEN_G, '3 + 4')
[ '3', '+', '4' ]

> tokenize(TOKEN_GY, '3x + 4')
[ '3' ]
> tokenize(TOKEN_G, '3x + 4')
[ '3', '+', '4' ]

最近更新于0001-01-01