Efficient regex for Canadian postal code function

User kind, postal code strict, most efficient format:

/^[ABCEGHJ-NPRSTVXY]\d[ABCEGHJ-NPRSTV-Z][ -]?\d[ABCEGHJ-NPRSTV-Z]\d$/i

Allows:

• h2t-1b8
• h2z 1b8
• H2Z1B8

Disallows:

• Z2T 1B8 (leading Z)
• H2T 1O3 (contains O)

Leading Z,W or to contain D, F, I, O, Q or U

Add anchors to your pattern:

var regex = /^[A-Za-z]\d[A-Za-z][ -]?\d[A-Za-z]\d$/;

^ means "start of string" and $ means "end of string". Adding these anchors will prevent the C from slipping in to the match since your pattern will now expect a whole string to consist of 6 (sometimes 7--as a space) characters. This added bonus should now alleviate you of having to subsequently check the string length.

Also, since it appears that you want to allow hyphens, you can slip that into an optional character class that includes the space you were originally using. Be sure to leave the hyphen as either the very first or very last character; otherwise, you will need to escape it (using a leading backslash) to prevent the regex engine from interpreting it as part of a character range (e.g. A-Z).