Simple regex expression to find capital letters is returning small letters

Question

I'm expecting this simple Regex expresison to return null since there are no capital letters in

 var a = "hiho"; var res = a.match(/[AZ]/gi); alert(res) 

the string.

Yet, it is returning an array of each small letter.

Why?

Answer 1

You're using the ignoreCase ( i ) flag, which makes your regex case-insensitive . Remove it and your regex should work as intended.

var res = a.match(/[A-Z]/g);

Answer 2

In the expression

/[A-Z]/gi

The "i" means "case insensitive", which is why both lower and upper case are matching.