I've contributed to a little JS lib [1] that takes a similar approach, but expands all of its predicates with two modifiers: a `maybe` modifier that tolerates n

I've contributed to a little JS lib [1] that takes a similar approach, but expands all of its predicates with two modifiers: a `maybe` modifier that tolerates null and undefined; and a `verify` modifier that throws if the predicate returns false. I've found it quite useful for eradicating some common boilerplate from my code. e.g.: var check = require('check-types'); check.unemptyString(''); // returns false check.maybe.unemptyString(); // returns true check.verify.unemptyString(''); // throws Error check.verify.maybe.unemptyString(); // doesn't throw [1] https://github.com/philbooth/check-types.js https://github.com/philbooth/check-types.js