conformist

A flatland-inspired schema definition and validation library for javascript.

Types

conformist ships with the following built-in type hierarchy:

Type
 |
 +-----------+
 |           |
Scalar      Container
 |           |
 |           +------+
 |           |      |
 |          List   Map
 |
 +-----+------+------+
 |     |      |      |
Num   Str    Bool  Enum
 |
 +
 |
 Int (TODO: Float)

Only the leaf nodes are concrete.

Scalars

Scalars are single-valued types.

Str is a string.

Bool is a boolean.

Int is an integer.

Enum is an enumerated set of Scalars: Enum.of(Str).valued(['a', 'b', 'c']).

Containers

Containers have multiple children.

List represents an array.

Map represents an object.

Schema

You compose types into schema. For example, if you want a number and a checkbox to enforce that the number is odd:

let NumberOddity = Map.of(
    Int.named('number'),
    Bool.named('mustBeOdd').using({optional: true})
).validatedBy(x => x.members.mustBeOdd.value
    ? x.members.number % 2 == 1
    : true)

Class cloning

Each Schema type has several class-cloning static methods on it. Ultimately, each of these calls Schema.clone in order to return a new, composed class with a modified prototype. These are:

Schema.named(name)

This assigns a name to the element

Schema.validatedBy(...validators)

This assigns 1 or more validators to the element.

Schema.using(overrides)

This assigns any number of overrides to the new prototype.

Schema.using({name}) is equivalent to Schema.named(name).

Elements

Elements are just instances of Schema types. let element = new Schema(). Elements have a few useful properties. Consider:

let element = new Str();
element.value
// undefined
element.set(3)
// true
element.value
// '3'
element.raw
// 3

Validators

Validators are functions. The idiomatic definition of a validator is a function that takes a validation message and returns a validation function from (element, context) to success. If the validation fails, the error message should be added to the element's errors.

function MustBeOdd(msg) {
    return (element, context) => {
        if (element.members.mustBeOdd.value) {
            if (!(element.members.number.value % 2)) {
                element.addError(msg);
                return false;
            }
        }
        return true;
    }
}
 
let NumberOddity = Map.of(
    Int.named('number'),
    Bool.named('mustBeOdd').using({optional: true})
).validatedBy(MustBeOdd);
 
let no = new NumberOddity();
no.set({number: 2, mustBeOdd: true});
// true
no.validate();
// false
no.errors
// ['You should enter an odd number']
no.allErrors
// {self: ['You should enter an odd number'], children: [number: [], mustBeOdd: []]}

Each element in a schema contains a list of errors, which starts out as undefined, but after validation is an array. Elements also have an allErrors property, which for Scalar elements is identical to the errors, but for Containers it will include errors for all children as well. For a List, allErrors returns a list of lists. For a Map, the errors are returned in the format:

{
    self: this.errors,
    children: {
        child1: this.members.child1.allErrors,
        child2: this.members.child2.allErrors,
        ...
    }
}

TODO

• drastically improve the quality of this README.
• organize code into separate files
• organize tests into suites
• make a decision about how to integrate with immutable
• should optional be a thing, or should there be a Required Validator? -- how to get useful "this element is required" messages, essentially.

Contributing

Please fork and send pull requests. If you add a feature, add a test. If you fix a bug, add a test. Thanks!

Authors

• Eric O'Connell [e-mail]

License

See LICENSE.