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How do I use regex for an integer range from 18-99?

I'm trying to create a javascript regex for a Google Form to validate an answer for an age related question. I want the user to only be able to enter whole number values between 18 and 99.
These values must be numerical only, cannot lead with zero(s), be negative, or include decimals. They must be whole positive numbers only.
I'm very new to regex this is my best attempt.
(1[89]|[2-9][0-9])
\d(1[89]|[2-9][0-9])
The first attempt will keep answers within my range (18 to 99) however it allows values with decimals, preceding zeros, and even trailing letters.
Second attempt when I use \d It only seems to accept values that lead with a zero despite if they include a decimal or trailing letter.

Then you can make a capture group like this ;
^(1[89]|[2-9][0-9])$
https://regex101.com/r/m2icLR/1

You can Try ^.{18,99}$
Explanation:
. dot stands for all characters. Except \n for which you will have to use s DOTALL flag.

Get integer number using regex in javascript

I am trying to write a regex to get only integer numbers e.g, 23, 234, 45, etc, and not select numbers with decimal points.
For Context :
I need it in a larger regex that I am writing to convert mixed fraction latex input
For example:
5\frac{7}{8}
But it should not select latex such as:
3.5\frac{7}{8}
The regex That I have so far is:
(^(.*)(?!(\.))(.*))\\frac{([^{}]+(?:{(?:[^{}]+)}|))}{([^{}]+(?:{(?:[^{}]+)}|))}
But it is for integer and decimal numbers alike. Need to change the regex for group1.

Maybe this will do it for you:
(?<!\d\.)\b(\d+)\\frac{([^{}]+(?:{(?:[^{}]+)}|))}{([^{}]+(?:{(?:[^{}]+)}|))}
It captures an integer expression before \fraq, unless it's preceded by a digit and a full stop.
(?<!\d\.) This ensures the number isn't preceded by a digit followed by a full stop, i.e.
the integer part of a floating.
\b Must be at the start of a number (to make sure we don't get a match with the end
of a multi digit number).
(\d+) Captures the integer number
\\frac Matches the string "\fraq"
The rest is the same as you original expression.
See it here at regex101.
Edit
Since there obviously are people out there, however unbelievable, that still haven't moved to a real browser ;) - the answer has to change to:
It depends of the syntax of latex, whether you can do it or not.
(And since I don't know that, I shouldn't have said anything in the first place ;)
The problem is that, without look behinds, you can't do it without matching characters outside the expression your interested in. In your regexr-example you clearly show that you want to be able to match expression not only at the beginning of strings, but also in the middle of the. Thus we need to be able to tell that the part before our match isn't the integer part of a decimal number. Now, doing this with matching isn't a problem. E.g.
(?:^|[^\d.])(\d+)\\frac{...
like Wiktor suggested in comments, will match if the expression is on the start of the line (^), or is preceded by something that isn't a decimal point or a digit ([^\d.]). That should do it. (Here at regex101.)
Well, as pointed out earlier, it depends on the syntax of latex. If two expressions can be directly adjacent, without any operators or stuff between them, you can't (as far as I can tell) do it with JS regex. Consider 1\fraq{0}{1}2\fraq{2}{3} (which I have no idea if it's syntactically correct). The first expression 1\fraq{0}{1} is a piece of a cake. But after that has been matched, we'd need to match a character before the second expression to verify the it doesn't start with a decimal number, but since the first expression already ate the characters, we can't. Because the test (?:^|[^\d.]) to verify that our expression doesn't start with a decimal number, would match one of the characters that actually belongs to our expression (the 2 in 2\fraq{2}{3}), thus making the match fail, because the remaining part doesn't start with the digit needed to satisfy the rest of the regex (\d+)\\frac{....
If, however, an expression always starts the string tested, or is preceded by and operator, or such, then it should be possible using
(?:^|[^\d.])(\d+)\\frac{([^{}]+(?:{(?:[^{}]+)})?)}{([^{}]+(?:{(?:[^{}]+)})?)}
Here at regex101.
(Sorry for my rambling)

Custom email regexp

I trying to create custom email regexp
[first]#[second].[third]
Allowed signs are numbers, letters and some special characters (I have done it)
One #
First+second to be from 1 to 20 characters long.
Email can't start or end with dot. Two or more dots next to each other are also not
allowed.
Third string to be 2 or 3 characters long.
This is what I have so far:
^(?!\.)(?=[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+#[a-zA-Z0-9]).{2,21}(?:\.[a-zA-Z0-9].{2,3})$
Unfortunately it doesn't work as I expected. Thanks for any tips.
For instance I can add multiple dots next to each other:
test...s#fm.com

Never ever write a regex to check for e-mails. You'll never make it right. As an example you say:
Allowed signs are numbers, letters and some special characters (I have done it)
which is terribly wrong, because you're then not including unicode characters like å or ţ which are valid. I'm also pretty sure you don't know that # is a valid value within the first part of an e-mail.
Third string to be 2 or 3 characters long.
and what about matching the following tlds: .info, .ninja, .website or .space?
So please, don't.
for reference:
https://davidcel.is/posts/stop-validating-email-addresses-with-regex/
http://stackoverflow.com/questions/23471591/regex-for-iban-allowing-for-white-spaces-and-checking-for-exact-length/23471740#23471740
http://thedailywtf.com/articles/how-to-validate-a-url

Following regex might help you.
^(([^<>()\[\]\\.,;:\s#"]+(\.[^<>()\[\]\\.,;:\s#"]+)*)|(".+"))#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,3}))$
Please read answer posted by #zmo too.

javascript regex : possible to have a range in the quantifier? [duplicate]

I've written a regular expression that matches any number of letters with any number of single spaces between the letters. I would like that regular expression to also enforce a minimum and maximum number of characters, but I'm not sure how to do that (or if it's possible).
My regular expression is:
[A-Za-z](\s?[A-Za-z])+
I realized it was only matching two sets of letters surrounding a single space, so I modified it slightly to fix that. The original question is still the same though.
Is there a way to enforce a minimum of three characters and a maximum of 30?

Yes
Just like + means one or more you can use {3,30} to match between 3 and 30
For example [a-z]{3,30} matches between 3 and 30 lowercase alphabet letters
From the documentation of the Pattern class
X{n,m} X, at least n but not more than m times
In your case, matching 3-30 letters followed by spaces could be accomplished with:
([a-zA-Z]\s){3,30}
If you require trailing whitespace, if you don't you can use: (2-29 times letter+space, then letter)
([a-zA-Z]\s){2,29}[a-zA-Z]
If you'd like whitespaces to count as characters you need to divide that number by 2 to get
([a-zA-Z]\s){1,14}[a-zA-Z]
You can add \s? to that last one if the trailing whitespace is optional. These were all tested on RegexPlanet
If you'd like the entire string altogether to be between 3 and 30 characters you can use lookaheads adding (?=^.{3,30}$) at the beginning of the RegExp and removing the other size limitations
All that said, in all honestly I'd probably just test the String's .length property. It's more readable.

This is what you are looking for
^[a-zA-Z](\s?[a-zA-Z]){2,29}$
^ is the start of string
$ is the end of string
(\s?[a-zA-Z]){2,29} would match (\s?[a-zA-Z]) 2 to 29 times..

Actually Benjamin's answer will lead to the complete solution to the OP's question.
Using lookaheads it is possible to restrict the total number of characters AND restrict the match to a set combination of letters and (optional) single spaces.
The regex that solves the entire problem would become
(?=^.{3,30}$)^([A-Za-z][\s]?)+$
This will match AAA, A A and also fail to match AA A since there are two consecutive spaces.
I tested this at http://regexpal.com/ and it does the trick.

You should use
[a-zA-Z ]{20}
[For allowed characters]{for limiting of the number of characters}

Javascript RegEx - Enforcing two max-lengths

It's been a while that I am juggling around this. Hope you can give me
some pointers.
All I want to achieve is, the string should contain EXACTLY 4 '-' and 10 digits in any giver order.
I created this regex : ^(-\d-){10}$
It does enforce max-length of 10 on digits but I am not getting a way to implement max-length of 4 for '-'
Thanks

Ok, here's a pattern:
^(?=(?:\d*?-){4}\d*$)(?=(?:-*?\d){10}-*$).{14}$
Demo
Explanation:
The main part is ^.{14}$ which simply checks there are 14 characters in the string.
Then, there are two lookaheads at the start:
(?=(?:\d*?-){4}\d*$)
(?=(?:-*?\d){10}-*$)
The first one checks the hyphens, and the second one checks the digits and make sure the count is correct. Both match the entire input string and are very similar so let's just take a look at the first one.
(?:\d*?-){4} matches any number of digits (or none) followed by a hyphen, four times. After this match, we know there are four hyphens. (I used an ungreedy quantifier (*?) just to prevent useless backtracking, as an optimization)
\d*$ just makes sure the rest of the string is only made of digits.