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I'm trying to make a regexp where it has to match a name like: John Smith. The only rules are first and last name should start with capital letter and has to be at least 2 characters long. Also the last name has a limit of 20 characters maximum and there's a a or white space between the names. So far I have this:

/[A-Z][a-z]+(\s|,)[A-Z][a-z]{19}/

It doesn't work when I tested it in this site: .html. I'm not sure what I missed. Any ideas?

I'm trying to make a regexp where it has to match a name like: John Smith. The only rules are first and last name should start with capital letter and has to be at least 2 characters long. Also the last name has a limit of 20 characters maximum and there's a a or white space between the names. So far I have this:

/[A-Z][a-z]+(\s|,)[A-Z][a-z]{19}/

It doesn't work when I tested it in this site: http://www.regular-expressions.info/javascriptexample.html. I'm not sure what I missed. Any ideas?

• javascript
• regex

Share Improve this question Follow edited Feb 24, 2012 at 16:57 Ben Lee 53.4k1515 gold badges128128 silver badges146146 bronze badges asked Feb 24, 2012 at 16:25 user977151user977151 50555 gold badges99 silver badges1818 bronze badges 5

• 2 (1) "Doesn't work" is never a sufficient problem description. (2) Why aren't you just using your browser console for testing the regex? – Matt Ball Commented Feb 24, 2012 at 16:28
• 1 @MДΓΓБДLL, actually, I think regex is the exception where "doesn't work" is a valid problem description. In this domain, it implicitly means "doesn't match what I intend it to match" and he explained exactly what he intended it to match. – Ben Lee Commented Feb 24, 2012 at 16:32
• 1 That’s a really terrible terrible approach, you know. It’s hopelessly naïve. Consider it will fail on any and all of Renée Fleming, Tim O’Reilly, John Paul Jones, William MᶜKinley, Malcolm X, Cher, Dominique Strauss-Kahn, Federico Peña, François Mitterand, Nicolae Ceaușescu, Chiang Kai-shek, María José Márquez, José María Juárez, or Federico del Sagrado Corazón de Jesús García Lorca. – tchrist Commented Feb 24, 2012 at 16:42
• It's only for homework guys. The teacher only specifies those requirements so it's not my idea to make it simple. But thanks for all your ideas:) – user977151 Commented Feb 24, 2012 at 16:56
• @user977151, in general it's a good idea to add the tag "homework" when you are posting help with homework problems. – Ben Lee Commented Feb 24, 2012 at 16:58

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6 Answers 6

Sorted by: Reset to default 3

Change the {19} to {1,19}. By itself, {19} means "match exactly 19 of the previous character". {1,19} means "match between 1 and 19 of the previous character".

/[A-Z][a-z]+(\s|,)[A-Z][a-z]{1,19}/

UPDATE: People are menting that this does not meet your requirements. As you described them, it's possibly a naive implementation of your requirements, but it is just your original implementation with the bug fixed. If you are actually looking for names, a less naive implementation might be:

/^[A-Z][-'a-zA-Z]+,?\s[A-Z][-'a-zA-Z]{0,19}$/

This will catch names with apostrophes or dashes, allows a space after the ma between the names if they are separated by a ma, and allows for single-letter last names. But as the menters have pointed out, this still fails to match a bunch of legitimate names and matches stuff that is definitely not name-like.

It also adds anchors ^ and $ to mean the entire string must match. If you are looking for a substring, you can remove those anchors and add in word boundary checks instead:

/\b[A-Z][-'a-zA-Z]+,?\s[A-Z][-'a-zA-Z]{0,19}\b/

You need {0,19} not just {19}. The latter means "exactly 19 chars".

"John Smith".match(/^[A-Z][a-z]{0,19}[\s,][A-Z][a-z]{0,19}$/)

Of course, this regexp doesn't match many totally valid names like "José Ortega y Gasset" or "Charles de Batz-Castelmore d'Artagnan".

Depending upon how long acceptable surnames can be, you can replace "{0,19}" with "{1,19}" or "{2,19}". The same applies to first names.

/^[A-Z][a-z]+[\s|,][A-Z][a-z]{1,19}$/.test("John Smith") // true

The {19} means that the last name must have exactly 19 lowercase characters after the first uppercase character.

This should work for you

\b[A-Z]+.+[?^ ][A-Z].{1,19}|\b[A-Z]+.+[?^,][A-Z].{1,19}

This starts with the beginning of a word, checks that the first letter is caps, matches the first word up to a white space or ma, then checks to make sure the first letter of the next word is capitalized, and matches everything up to 19 characters after that. Also makes sure each name is 2 or more characters long.

Here are some expressions that might help for more plex names

(^[A-Z][a-z]*$) - A typical First Name or Last Name like Thomas
(^[A-Z][a-z][A-Z][a-z]*$) - names like McDonald
(^[A-Z][a-z]*(-|\s)[A-Z][a-z]*$) - names like Tonya-Smith or Tonya Smith
(^[A-Z]('|’)[A-Z][a-z]*$) - names like Tim O’Reilly
(^[a-z]+\s[A-Z][a-z]*$) - names like von Gogh

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