shouldbe

Error-throwing type-checking for JavaScript

shouldbe is a type-checking utility for JavaScript code that lives write in your code and throws up if underscore says the value is not of the given type.

shouldbe("string", str) // throws if _.isString(str) would return false

Underscore is the only dependency right now.

Just add the relevant mixin to underscore.

For example:

_.mixin({
    isEvenValue: function (val) { return !(val % 2); }
});
shouldbe("even-value", 3); // throws up!