How can I write a regex to match something which is neither a letter or a digit?

I'm trying this

str = "bla";
/([^A-z]|[^0-9])/.tes开发者_StackOverflowt(str.charAt(0));

but it gives me true no matter what I put in the string

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It's because your regex means "anything that is either not a letter or not a number." All characters satisfy at least one of those conditions. I suspect what you really want is this:

/[^A-Za-z0-9]/

This means "anything that is both not a letter and not a number." See the difference?

As a side note, [A-z] is incorrect. [A-Z] and [a-z] are two distinct character sets, and there is technically not a defined continuation between them. Some regex engines will let you get away with this, but some will throw an error or do something you didn't intend.

The correct way to write "any letter from A to Z, regardless of case" is [A-Za-z]. Or you could use the i flag to make your regex case-insensitive, which in your case would be:

/[a-z0-9]/i