1. Lazy Matching
For example, Hi+? will only match Hi in Hiiiii.
'Hiii'.replace(/Hi+?/, 'x') // xii
'Hiii'.replace(/Hi+/, 'x') // x
'Hellollo'.replace(/H.*?llo/, 'x') // xllo
'Hellollo'.replace(/H.*llo/, 'x') // x
'yoooooo'.replace(/yo{2,6}?/, 'x') // xoooo
'yoooooo'.replace(/yo{2,6}/, 'x') // x
2. Word Boundaries
'How are you?'.replace(/\b.+?\b/, 'x') // x are you?
3. Capturing Group Reference
Capturing group format: (xxx), backreference: \n, such as: \1, \2, etc.
'How are you?'.replace(/(how)/i, '$1 old') // How old are you?
'1#2#3'.replace(/^(\d)#(\d)#(\d)$/i, '$1 $2 $3') // 1 2 3
'111#111#111'.replace(/^(\d+)#\1#\1$/i, '$1') // 111
4. Named Capturing Group + Backreference
Named capturing group: (?<name>xxx), backreference: \k<name>
'111#111'.replace(/^(?<num>\d+)#\k<num>$/i, '$<num>') // 111
5. Lookahead and Lookbehind
Including:
- Positive lookahead:
(?=xx) - Negative lookahead:
(?!xx), negative means cannot match - Positive lookbehind:
(?<=xx) - Negative lookbehind:
(?<!xx), negative means cannot match
6. Modifiers
In addition to the commonly used g for global matching and i for case-insensitive matching:
m: multiline shorthand, enables multiline matching, treats^and$as the start and end of lines.u: unicode shorthand, allows the use of Unicode code point escapes.y: sticky shorthand, enables sticky matching, attempts to match from the last match position.
7. Second Argument of replace
If it is a string, you can use the following special characters:
$n: 1<=n<=99, matches the text captured by the 1st to 99th group.$&: The matched substring.- `$``: The portion of the string that precedes the matched substring.
$': The portion of the string that follows the matched substring.$$: The dollar sign.$<name>: The result value of the named capturing group.
If it is a function, the return value of the function is used as the replacement string. The function follows the following rules:
- The first argument is the matched substring, corresponding to
$&mentioned above. - The 2nd to n+1th arguments correspond to the 1st to nth capturing group (if any).
- The n+2th argument is the offset, the offset of the matched substring in the original string.
- The n+3th argument is the original string being matched.
- The n+4th argument is the object that matches the named capturing group.