blazon

A small, fast, non-trivial, dependency-free, non-stick, fully-franked, run-time type checker with an idiomatic API.

HERALDRY

Describe or depict (armorial bearings) in a correct heraldic manner.

Example:

Creating Types:

var blazon = require('blazon');
var { Maybe, Custom } = blazon;

const Email = blazon(blazon.And(
    String,
    Custom(value =>
        value.match(/^.+@[^.].*?\..*[^.]$/) ? value : throw new Error('Value must be an email')
    )
));

const User = blazon({
    firstName: String,
    surname: String,
    email: Maybe(Email),
    nickname: Maybe(String, 'Buddy'),
    age: Number
});

function greetUser(maybeNotAValidUser){
    // Throws if invalid.

    var user = User(maybeNotAValidUser);

    // user is valid at this point.
}

Friggin' fast

On an i7 laptop:

100,000 non-trivial Types can be defined in ~700ms

100,000 non-trivial passing checks can be performed in ~130ms

10,000 non-trivial failing checks can be performed in ~37ms

Available base types (BaseType):

value type constructors are valid, eg:

String, Number, Boolean

Extra types provided by blazon:

List(Type[, minLength, maxLength)

Ensure every item in array matches Type, and optionally, that the length is between a min and max.

Maybe(Type, default<optional>)

Ensure a value is either Type or null/undefined.

And(Types...)

Ensures a value is every one of Types.

Or(Types...)

Ensures a value is any one of Types.

Exactly(value)

Ensures a value is exactly value

Cast(BaseType) OR Cast(sourceType, targetType, fn customConverer(value, target))

Casts a value to a BaseType OR Casts from anything to anything with a customConverter.

Custom(fn<value, target, trace>)

Ensures fn(value) does not throw.

The value returned from fn will be the result of the type instantiation.

ensure(types..., function)

Create a function which only accepts specifically typed arguments.