How to get the first letter from the current file for a VSCode snippet?

Question

I'm trying to get the first letter from the current file in order to create a snippet that should look like:

const f = new Object()

Where f is the first letter of the current file. I know I can access to the file name by using TM_FILENAME_BASE, but how can access to the first letter only?

Answer 1

"body": ["${TM_FILENAME_BASE/(.).*/$1/}"],

(.) capture the first character in group 1
.* match the rest, you won't use this later but you do want to match it
$1 replace the entire match with just the first capture group

In general, you are looking for snippet variable transforms.