Something wrong with expression node

In a “column list loop”, I would like to count the values -9999. My column is an integer. But when I put

if($[currentColumnName] = -9999, 1, 0)

indicate by K-IA !!

it tells me

Operator ‘==’ is not applicable for STRING and INTEGER

When I put

if($$[“currentColumnName”] => ‘-9999’,1,0)

nothing comes out (no 1 in the row)

I even tried

if(join(“”,“$[\‘’,string($$currentColumnName),”\“]”) = -9999,1,0)

How can I count these -9999 values in my column?

thx for your help, I hope this is more useful than the AI 😄