isFalsy

Tests for Falsy by simply applying negation ! to the tested val.

The value is mostly in added type-information and explicity, but in case of this simple type much the same can often be archived by just using negation !:

@example

const consumer = (value: boolean | Falsy) => {
    if (!value) {
        return ;
    }
    type newType = typeof value; // === true
    // do stuff
  };

const isFalsy: (val: unknown) => val is Falsy;