Negation Matching in JavaScript Regular Expression

Question

I have yet another javascript regex question.

I need to match any line that does not start with three letters and a pipe.

For instance, in

some text that doesn't matter
Test1
RandomLine
C|
FName

Test1, RandomLine, C|, FName must all be matched.

However,

some text that doesn't matter
TST|
MST|
RAD|

must not be matched.

Note: The above mentioned test cases are one string altogether and not 3 different strings

I was trying to come up with the logic and this was what I arrived at:

/\n.{3}\|/g

However, I need a way to be able to negate the .{3}\| in my regex, since I need to find a newline that is not followed by 3 characters and a pipe.

I did go through the site and I read that I may have to use the negative lookaheads to achieve negations but I was unable to achieve any success with that.

Is there any way to be able to accomplish this in JavaScript?

Thanks.

Answer 1

You need to use negative lookahead here:

^(?!((TST|MST|RAD)[|]|some text)).*$