Regex "And" operation

Regex "Or" operation is obvious.

This is a example

^abc$|^123$

This will match abc or 123. 

But how do you do a regex "and"

You may write something like this:

^abc$&^123$

Wrong, this is totally wrong. There is not "&" operator in regex.

Is it possible to do an "And" operation in regex? 

The answer is "YES".

That leads us to the power regex look around feature. 

For "And" operation, what we need is the positive look ahead.

(?m)^(?=.*[A-Z].*)(?=.*[a-z].*)(?=.*?[0-9].*)[^1]*$

Have a look example above. 

Look head matches, but doesn't take space, That means, the regex after the look ahead will start matching from the beginning as well.

In this example, the only matched string will be Abcd5234. 

Abcd1234

ABCD1234

abcd1234

abcdabcd

aBcd1234

aBcdabcd

Abcd5234

Why?

Because this string must match ^(?=.*[A-Z].*), means at least 1 Capital letter. 

Also, it must match (?=.*[a-z].*), one lowercase letter. 

Also, it must match (?=.*?[0-9].*), one number

and lastly, it must match [^1]*, no "1" included.

--
Feng