Had to escape it with a backslash, otherwise JavaScript would think it is the pattern end. We can see one common rule in these examples: the more precise is the regular expression — the longer and more complex it is.
In real life both variants are acceptable. In this task we do not need other color formats like or rgb 1,2,3 etc. A hexadecimal character can be described as [a-fA-F].
Or if we use the i flag, then just [a-f]. We want to make this open-source project available for people all around the world. See this page for more detail. See also universal solution via lookahead: Restricting Character length in Regular expression — Vadzim. Add a comment. Active Oldest Votes. You can use curly braces to control the number of occurrences. Improve this answer. Joren Joren Diego Sevilla Diego Sevilla Rochdi Belhirch Rochdi Belhirch 61 1 1 bronze badge.
This allows for whitespace which was not asked for. Sign up or log in Sign up using Google. The following regex is very similar to the previous example of limiting the number of nonwhitespace characters, except that each repetition matches an entire word rather than a single, nonwhitespace character. It matches between 10 and words, skipping past any nonword characters, including punctuation and whitespace:.
If you want to count words that contain non-ASCII letters and numbers, the following regexes provide this capability for additional regex flavors:. As noted, the reason for these different but equivalent regexes is the varying handling of the word character and word boundary tokens explained in Word Characters in Recipe 2.
Each repetition of the noncapturing group in the first two of these three regexes matches an entire word followed by zero or more nonword characters. Without the word boundary, a single repetition would be allowed to match any part of a word, with subsequent repetitions matching additional pieces. It uses a plus one or more instead of an asterisk zero or more quantifier, and explicitly allows matching zero characters only if the matching process has reached the end of the string.
Unfortunately, none of these options allow JavaScript or Ruby 1. A possible workaround is to reframe the regex to count whitespace rather than word character sequences, as shown here:. If the multiline flag is set to true, also matches immediately after a line break character. Note: This character has a different meaning when it appears at the start of a group.
Matches the end of input. If the multiline flag is set to true, also matches immediately before a line break character. Matches a word boundary. This is the position where a word character is not followed or preceded by another word-character, such as between a letter and a space.
Note that a matched word boundary is not included in the match. In other words, the length of a matched word boundary is zero. Matches a non-word boundary. This is a position where the previous and next character are of the same type: Either both must be words, or both must be non-words, for example between two letters or between two spaces. The beginning and end of a string are considered non-words. Same as the matched word boundary, the matched non-word boundary is also not included in the match.
Lookahead assertion: Matches "x" only if "x" is followed by "y". However, neither "Sprat" nor "Frost" is part of the match results. Negative lookahead assertion: Matches "x" only if "x" is not followed by "y". Lookbehind assertion: Matches "x" only if "x" is preceded by "y".
However, neither "Jack" nor "Tom" is part of the match results. Negative lookbehind assertion: Matches "x" only if "x" is not preceded by "y". Groups and ranges indicate groups and ranges of expression characters.
Matches either "x" or "y". A character class. Matches any one of the enclosed characters. You can specify a range of characters by using a hyphen, but if the hyphen appears as the first or last character enclosed in the square brackets it is taken as a literal hyphen to be included in the character class as a normal character.
For example, [abcd] is the same as [a-d].
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