Formation.js

Rules plus Values equals Results

Formation.js is a simple validation engine that exposes validate(rules: Rules, values: Values): Results function. See type definitions below.

Type Definitions

Value

export type Value = boolean | number | string | Object | null

Value is something that we might want to validate, it can be one of following types: boolean, number, string, Object or null. By convention null is used for to denote empty or default values. When input field has nothing in it, or radio button is neither selected nor deselected - it‘s empty.

Message

type Message = string Message is a string, In real life application message should be an id pointing to i18n/l10n bundle.

Validation

type Validation = (value: Value) => ?Message

Validation is a function that accepts Value and returns Message or null (Maybe Message).

Result

type Result {value: Value, messages: Message[]}

Result structure contains value and list of messages, empty list of messages means that result is valid.

Rule

export type Rule = {validations: Validation[], defaultValue: Value, required: boolean}

Rule structure contains list of validation functions, default value if any and required flag. Rule can be executed against Value to produce Result.

Rules

type Rules = {[string]: Rule}

Rules structure is a map of keys and rules.

Values

type Values = {[string]: Value}

Values structure is a map of keys and values.

Results

type Results = {[string]: Result}

Results structure is a map of keys and results