I'm trying to create a regex that doesn't allow digits or spaces in the beginning. I've tried doing something like this:
^[\S][\D][\w+_.-]+@{1}[\w_.-]+\.{1}[a-zA-z]*$
However, when I use 4test@example.com it says it's an email, but when I use 4test@example.com it says it's not an email. In both cases, I'd like for it to say it's not an email. There shouldn't be a space or digit, how can I combine these two: [\S][\D] so that it works correctly?
In your pattter \S will match any non whitespace char and it will also match a digit.
As mentioned in the comment, you can exclude matching the digit using a negated character class. If If you repeat the character class after that 1+ times the part before the @ should contain at least 2 characters.
If the minumum should be 1 char, you could use a * instead of a +.
Note that you don't need {1} and that [a-zA-z] can match more than [a-zA-Z]
If you repeat the character class [a-zA-Z]* at the end 0+ times using * the match could possibly also match a dot only.
You could update the pattern to:
^[^\d\s][\w_.-]*@[\w_.-]+\.[a-zA-Z]+$
If using \S is too broad, another option could be using a negative lookahead asserting not a digit followed by repeating the character class 1+ times:
^(?!\d)[\w_.-]+@[\w_.-]+\.[a-zA-Z]+$
