Another regex expression - regex

Question

I need a regular expression for the next rules:
should not start or end with a space
should contain just letters (lower / upper), digits, #, single quotes, hyphens and spaces (spaces just inside, but not at the beginning and the end, as I already said)
should contain at least one letter (lower or upper).
Thank you

Answer 1

I think
^[^ ](?=.*[a-zA-Z]+)[a-zA-Z0-9#'\- ]*[^ ]$
should help you.

Answer 2

"Does it really matter guys?"
with regards to the dialect of regex: yes it does matter. Different languages may have different dialects. One example off the top of my head is that the RegEx library in PHP supports lookbehinds whereas RegEx library in JavaScript does not. This is why it is important for you to list the underlying language that you're using. Also for future reference, it is helpful for those wanting to answer your questions to provide us with sample input and sample matches from the input.
Using the information that you provided, this is also a question that I feel as though you should use RegEx and JavaScript to validate the input. Take a look at this example:
window.onload = function() {
var valid = "a1 - 'super' 1";
var invalid1 = " a1 - 'super' 1"; //leading ws
var invalid2 = "a1 - 'super' 1 "; //trailing ws
var invalid3 = "a1 - 'super' 1?"; //invalid (?) char
var invalid4 = "1 - '123'"; //no letters
console.log(valid + ": " + validation(valid));
console.log(invalid1 + ": " + validation(invalid1));
console.log(invalid2 + ": " + validation(invalid2));
console.log(invalid3 + ": " + validation(invalid3));
}
function validation(input) {
var acceptableChars = new RegExp(/[^a-zA-Z\d\s'-]/g);
var containsLetter = new RegExp(/[a-zA-Z]/);
return input.length > 1 && input.trim().length == input.length && !acceptableChars.test(input) && containsLetter.test(input);
}