Question

Hello I need help with validation using regular expressions in javascript

I need something like this.

The first character should be a designated character like A, B or C only. and the next 3 characters should be numbers.

example: A123, B345, C234.

D123 is not allowed.

Answer 1

This works for me:

var rgx = /^(?:A|B|C)\d{3}$/;

alert('A123'.match(rgx)); // A123
alert('D123'.match(rgx)); // null
alert('B986'.match(rgx)); // B986

Breakdown:

• ^ matches the beginning of a string
• (?:A|B|C) matches A or B or C but does not capture it
• \d{3} matches 3 digits in a row
• $ matches the end of the string

Therefore 'A12' would not be valid because there aren’t 3 digits, nor would ' A123' because of leading whitespace, nor would 'A123 hello' because the match isn’t at the beginning and end of string.

To make it case insensitive, add i after the / at the end of the regex.