How do I compare string and boolean in Javascript?

I got the Json "false" from server. I respond as bool but it's Json so it's in browser type is String instead of bool.

So if I run (!data) whenever I want to check "false" == false then they not worked.

So how can I parse bool from String in JavaScript then?

"true" == true and "false" == false. Then the code (!data) can check what it is [true and false]