regex ensure string starts and ends with digits

Question

How do I write a regular expression for use in JavaScript that'll ensure the first and last characters of a string are always digits?

r = /\D+/g;
var s = "l10ddd31ddd5705ddd";
var o = r.test(s);
console.log(o);

So, 1KJ25LP3665 would return true, while K12M25XC5750 would return false.

Answer 1

You can have a regex like below:

 /^\d(.*\d)?$/

• The ^ to begin match from start of the string and $ to continue match till end of the string.
• \d to match a digit at the beginning and the end.
• .* to match zero or more characters in between.
• We make the group 1 => (.*\d) optional with the ? metacharacter to optionally match zero or more characters ending with the digit till the end of the string. This would help if the string has only a single digit.