vahvista

Simple composable validation framework

License

vahvista is licensed under the MIT license.

Getting Started

Requirements

Under node.js, or a bundler such as webpack or rollup; vahvista has no additional requirement.

Installation

Bundler or node build

If you want to use vahvista with a bundler like webpack or rollup, or with node.js;

• Install vahvista with your favorite package manager;
  • npm; npm install --save-dev vahvista.
  • yarn; yarn add vahvista --dev
  • pnpm; pnpm add -D vahvista

Browser ready or CDN build

If you wish to use vahvista in an environment that does not use a bundler or modules; you have two options

• Download the vahvista.iife.js file from the latest release and include it in your project.
• Link to it from UNPKG CDN https://unpkg.com/vahvista/dist/index.iife.js or https://unpkg.com/vahvista@{version}/dist/index.iife.js. See UNPKG for more versioning options.
• Link to it from JSDELIVR CDN https://cdn.jsdelivr.net/npm/vahvista/dist/index.iife.js or https://cdn.jsdelivr.net/npm/vahvista@{version}/dist/index.iife.js. See JSDELIVR for more versioning options.

Basic validation

To use vahvista, simply import vahvista from "vahvista";. Or you may use a shorter name with import v from "vahvista";

vahvista is relatively simple to use for validation. It does provide any messaging feedback, but does allow you to chain a set of rules together and verify that a value passes those rules.

Does x = 4? v.equals(4)(x). Is x between 2 and 10 and an integer? v.integer.inRange(2, 10)(x) Is name an all lower-case alphabetic name? v.alphabetic.lowerCase(name).

Core concepts

vahvista is based on two concepts, rules and predicates. Although these concepts externally seem the same, one builds the other.

Rules

Rules are the basic building blocks of vahvista validation. Rules are used to build predicates and verify some aspect of a value to be tested. Rules are wrapped into predicates by vahvista and accessed via their names from vahvista itself.

Predicates

A predicate is any object from vahvista than can be called to verify a value. Predicates may also be chained to form new predicates that will ensure a value is verified by all rules in the predicate chain.

Rules

Type checks

Basic type checking rules.

• undefined: is the value undefined.
• null: is the value null.
• nil: is the value null or undefined.
• value: is the value a simple type such as boolean, number, bigint, or string or boxed instance.
• boolean: is the value a boolean or boxed Boolean instance.
• number: is the value a number of boxed Number instance.
• nan: is the value a NaN.
• symbol: is the value a symbol.
• arrayLike: is the value array-like, an object with length and indexed elements.
• array: is the value an Array.
• string: is the value a string or boxed String instance.
• arrayBuffer: is the value an ArrayBuffer instance.
• buffer: is the value a Buffer instance.
• dataView: is the value a DataView instance.
• typedArray: is the value one of the typed array, such as Uint32Array, Int32Array, Float64Array, etc.
• uint32Array: is the value an Uint32Array instance.
• uint16Array: is the value an Uint16Array instance.
• uint8Array: is the value an Uint8Array instance.
• int32Array: is the value an Int32Array instance.
• int16Array: is the value an Int16Array instance.
• int8Array: is the value an Int8Array instance.
• float64Array: is the value an Float64Array instance.
• float32Array: is the value an Float32Array instance.
• uint8ClampedArray: is the value an Uint8ClampedArray instance.
• function: is the value a function.
• regExp: is the value a RegExp instance.
• object: is the value an object.
• error: is the value an Error or derivative instance.
• date: is the value a Date instance.
• iterable: is the value an iterable object.
• iterator: is the value an Iterator implementation.
• promise: is the value a Promise instance or promise-like object.
• set: is the value a Set instance.
• weakSet: is the value a WeakSet instance.
• map: is the value a Map instance.
• weakMap: is the value a WeakMap instance.
• enum([...values]): is the value one of the provided values.
• typeOf(type): does the value identify as type with the typeof operator. Example are "string", "object".
• instanceOf(constructor): is the value an instance create by the provided class or constructor.

Values

Many values maybe compared with certain basic equality or relational comparisons. Such values include numbers and strings. Object references also may be strictly equal if a value references the exact same object.

• oneOf(...values): is the value one of the provided values.
• equal(target): is the value strictly equal to target.
• notEqual(target): is the value not strictly equal to target.
• greaterThan(target): is the value greater than target.
• greaterThanOrEqual(target): is the value greater than or equal to target.
• lessThan(target): is the value less than target.
• lessThanOrEqual(target): is the value less than or equal to target.

Boolean logic

The boolean rule can check whether a value is strictly a boolean value; or if they are truthy or falsy.

• true: is the value strictly true.
• truthy: is the value truthy.
• false: is the value strictly false.
• falsy: is the value falsy.

Numbers

• negative: is the value negative, meaning less than zero.
• positive: is the value positive, meaning greater than zero.
• finite: is the value finite, meaning not equal to Infinity or -Infinity.
• infinite: is the value infinite, meaning equal to Infinity or -Infinity.
• uint32: is the value within the range of the 32-bit unsigned integer, meaning inclusively between 0 and 4294967295.
• uint16: is the value within the range of the 16-bit unsigned integer, meaning inclusively between 0 and 65535.
• uint8: is the value within the range of the 8-bit unsigned integer, meaning inclusively between 0 and 255.
• int32: is the value within the range of the 32-bit signed integer, meaning inclusively between -2147483648 and 2147483647.
• int16: is the value within the range of the 32-bit signed integer, meaning inclusively between -32768 and 32767.
• int8: is the value within the range of the 32-bit signed integer, meaning inclusively between -128 and 127.
• integer: is the value an integer, meaning it has no fractional part.
• integerOrInfinite: is the value an integer or infinite.
• inRange(min, max): is the value inclusively between min and max.

Collections

Collection are objects that have enumerable elements within them. Examples would be array-like objects with indexed element within its length, objects with named enumerable elements or properties, and maps with keyed elements.

• empty: is the value empty, meaning it is not a collection or contains no enumerable elements.
• notEmpty: is the value not empty, meaning it contains one or more enumerable elements.
• size(n): does the value have n enumerable elements.
• maxSize(max): does the value have no more than max enumerable elements.
• minSize(min): does the value have at least min enumerable elements.

Array-like objects

Array-like objects are values or objects with a readable length property and indexed elements. One such value is a string. Arrays are definitely considered array-like, but objects may implement the semantics of an array.

• length(n): does the value have a length of n.
• maxLength(max): does the value have a length no greater than max.
• minLength(min): does the value have a length of at least min.

Arrays

• includes(...items): does the value include all the items.
• includesAny(...items): does the value include any of the items.

Strings

• alphabetic: is the value an alphabetic string.
• alphaNumeric: is the value an alpha-numeric string.
• dateLike: is the value a date-like string, meaning that it may be parsed with Date#parse.
• numeric: is the value a numeric string.
• integral: is the value an integer string.
• lowerCase: is the value a completely lower-case string.
• upperCase: is the value a completely upper-case string.
• url: is the value a URL, meaning it can be parsed with new URL.
• contains(target): does the value contain the target string.
• endsWith(target): does the value end with the target string.
• startsWith(target): does the value start with the target string.
• matches(expression): does the value match the regular expression.

Keyed collections

A keyed collection is any object that posses some means of access values based on a key. A key may be a string, number, or with certain collections such as Map, any kind of value. Objects and arrays may be considered keyed collects since some string or numeric value may be used as a key to another value of any kind. Sets may also be considered keyed collection since a value is its own key.

• has(...keys): does the value have all the specified keys.
• hasAny(...keys): does the value have any of the specified keys.

Errors

• evalError: is the value an EvalError or derivative instance.
• rangeError: is the value a RangeError or derivative instance.
• referenceError: is the value a ReferenceError or derivative instance.
• syntaxError: is the value a SyntaxError or derivative instance.
• typeError: is the value a TypeError or derivative instance.
• uriError: is the value an URIError or derivative instance.

Named objects

A named object is any object that has a name property. Some examples are functions, Errors, and Files.

• name(match): does the value name match the match string or regular expression.

Tuples

Tuples are collections of fixed length and element types. In JavaScript the closest thing to this would be an array of a specific length.

• tuple(...predicates): does the array have the exact number of elements matches the predicates.

Object shapes

shape(definition) tests whether a value conform to definition.

The definition may be composed of the following:

• An object which contains properties with other definitions or predicates.
• An array with a single element containing a definition or predicate.
• A single lone predicate.

An example shape definition could be:

shape({
    name:       v.string.notEmpty.maxLength(45),
    dataPoints: [v.integer.inRange(-256, 256)],
    meta:       v.object,
    style: {
        color:     v.enum(knownColors),
        fill:      v.enum(knownColors),
        thickness: v.number.finite,
    },
})

Custom rules

vahvista may be extended with custom rules. This is done with vahvista.register and vahvista.factory.

Basic rules

Basic rule do not require any additional information to verify a value. They are simply a function that receives the value and returns true if the value passes or false if it fails. An example of a basic rule may be one that ensure an ID value is a string containing a positive integer.

v.register("id", value => (/\d+/u).test(value));

Rules with inputs

If a rule needs more information to verify a value, they may be given arguments. Such rules must be created from a "rule factory". A rule factory is a function that accepts the information needed for the rule to do its job and returns that rule with the needed information. An example of such a rule may be one that verifies a date is later than another.

v.factory("after", date => value => toDate(dateTime).valueOf() < toDate(value).valueOf());
// use as `v.after(Date.now())(tomorrow)` which would be true.

TypeScript

vahvista works well with TypeScript since it was built in TypeScript. There is one caveat of using vahvista in TypeScript that you must contend with when adding custom rules. You must tell TypeScript the predicate for those rules now exist in vahvista. To do so, you must use interface declaration merging. An example using those the prior two examples:

v.register<string>("id", value => (/\d+/u).test(value));
v.factory<string|Date>("after", (date: string|Date) => value => toDate(dateTime).valueOf() < toDate(value).valueOf());

declare module "vahvista" {
    interface Rules<T> {
        id: Predicate<string>;
        after(date: string|Date): Predicate<string|Date>;
    }
}

Other things to note about rules registered in TypeScript;

• The generic argument for factory and register denote the expected input of the rule, though this is not guaranteed.
• The generic argument for Predicate is the confirmed type after being verified by the rule.
• The generic argument T for Rule is current type predicate chain.