Why's this "fuckshit" not working?

[Pranoy1c]

This gives me an empty array. I have tried using true, false, "lite" and all give empty array. I wanted to use this library for testing usernames containing profanity but this doesn't seem to work.

var profanity = require( 'profanity-util', { substring: true } );
console.log(profanity.check('fuckshit'));