Validia

A TypeScript-friendly validator.

🏁 Goal

This package provides:

• Compiler; It compiles schemas then creates a validation function. The validation is fast.
• Type Assertion; It can compute the value type of schemas. The validated values will get well typing.
• Customizable; You can use a function (with type guard) to define your validation.
• Localization; Every validation error is represented with a code and arguments. You can define error messages in your primary language. (Of course, this package provides the default error messages.)

💿 Installation

Use npm or a compatible tool to install.

npm install validia

📖 Usage

➡️ One-shot Validation

import { validate } from "validia";

// 1. Define your schema.
const myOptionSchema = {
  type: "object",
  properties: {
    include: { type: "array", elements: { type: "string" } },
    exclude: { type: "array", elements: { type: "string" } },
  },
} as const; // `as const` is important.

// 2. Validate a value.
declare let value: any;
validate(myOptionSchema, value);
// The `value` is `{ include?: string[]; exclude?: string[] }` here.

Schema is simple objects. But I'd like to recommend using factory functions to utilize input completion and ensure good typings.

➡️ Using Factory Functions

import { schemas as s, validate } from "validia";

// 1. Define your schema.
const myOptionSchema = s.object({
  include: s.array(s.string()),
  exclude: s.array(s.string()),
});

// 2. Validate a value.
declare let value: any;
validate(myOptionSchema, value);
// The `value` is `{ include?: string[]; exclude?: string[] }` here.

The schemas is the namespace of factory functions.

➡️ Compile Validation Functions

import { createValidation, schemas as s, Validate } from "validia";

// 1. Define your schema.
const myOptionSchema = s.object({
  include: s.array(s.string()),
  exclude: s.array(s.string()),
});

// 2. Compile validation.
const validate: Validate<typeof myOptionSchema> = createValidation(
  myOptionSchema
);

// 3. Validate a value.
declare let value: any;
validate(value);
// The `value` is `{ include?: string[]; exclude?: string[] }` here.

Unfortunately, you have to declare the type of the validate function explicitly because of microsoft/TypeScript#33580. In short, the type of Assertion Functions must be decided before the type inference phase.

➡️ For Legacy Platform

This package requires ES2018 or later.

If you want to use this package on a legacy platform, use the validia/es5 entry point along with core-js, @babel/runtime, and regenerator-runtime. For example:

const { schemas, createValidate } = require("validia/es5");
// ...

Or you can merely configure your bundler to transpile this package as well.

The generated code of createValidation(schema) function is ES5 then it works well on IE11. (probably!)

📚 References

import {
  // objects
  createValidation,
  validate,
  schemas,
  ValidationError,
  DefaultMessage,

  // types
  Message,
  Schema,
  TypeOf,
  Validate,
} from "validia";

➡️ function createValidation<T>(schema: T, options?: Options)

Compile the validation function of given schema object.

Parameters

• schema ... The schema object.
• options ... The options to compile.
  • options.defaultMessages ... The error message generator. Optional. Default is DefaultMessage.

Return Value

• The validation function of the schema; (value: any, options?: Options) => void.
  • If the value argument passed the validation, the value argument gets good typing. Otherwise, the validation function throws a ValidationError instance.
  • The options.messages argument is the error message generator. Optional. Default is options.defaultMessages.
  • The options.name argument will be used in error messages. Optional. Default is "value".

➡️ function validate<T>(schema: T, value: any, options?: Options)

This is equivalent to createValidation<T>(schema)(value, options).

➡️ object schemas

The schema factories.

• schemas.any() ... The schema representing any.
• schemas.array(schema?, options?) ... The schema representing specific arrays.
  • schema is the schema of array elements. Default is schemas.any().
  • options.maxLength is the maximum length.
  • options.minLength is the minimum length.
  • options.unique is the flag to disallow duplicated values.
• schemas.bigInt(options?) ... The schema representing specific bigint values.
  • options.maxValue is the maximum value.
  • options.minValue is the minimum value.
• schemas.boolean() ... The schema representing true or false.
• schemas.instanceOf(constructor) ... The schema representing instances of a specific class.
  • constructor is the class.
• schemas.custom(name, check) ... The schema representing a user-defined check.
  • name is the name of this check. It will be used in error messages.
  • check is the function of this chck; <T>(value: unknown) => value is T. Return true if the value passed validation.
• schemas.enum(...values) ... The schema representing any of specific values.
  • values is the list of allowed values.
• schemas.function() ... The schema representing any functions.
• schemas.number(options?) ... The schema representing specific numbers.
  • options.allowInfinity is the flag to allow Infinity and -Infinity.
  • options.allowNaN is the flag to allow NaN.
  • options.intOnly is the flag to disallow non-integers.
  • options.maxValue is the maximum value.
  • options.minValue is the minimum value.
• schemas.object(properties?, options?) ... The schema representing specific objects. If you give no arguments, the returned schema matches any objects.
  • properties is the definition of known properties; Record<string, Schema>.
  • options.allowUnknown is the flag to allow unknown properties.
  • options.required is true or the array of known property names to be required. If true, all known properties are required.
• schemas.record(schema?) ... The schema representing specific objects.
  • schema is the schema of properties. Default is schemas.any().
• schemas.string(options?) ... The schema representing specific strings.
  • options.maxLength is the maximum number of characters.
  • options.minLength is the minimum number of characters.
  • options.pattern is the regular expression of allowed strings.
• schemas.symbol() ... The schema representing any symbols.
• schemas.tuple(...elements) ... The schema representing specific tuples.
  • elements is the schemas of elements.
• schemas.anyOf(...schemas) ... The schema representing specific union types.
  • schemas is the schema of allowed types.
• schemas.bigInt64 ... Equivalent to schemas.bigInt({ maxValue: 9223372036854775807n, minValue: -9223372036854775808n }).
• schemas.bigUint64 ... Equivalent to schemas.bigInt({ maxValue: 18446744073709551615n, minValue: 0 }).
• schemas.null ... Equivalent to schemas.enum(null).
• schemas.int8 ... Equivalent to schemas.number({ intOnly: true, maxValue: 127, minValue: -128 }).
• schemas.int16 ... Equivalent to schemas.number({ intOnly: true, maxValue: 32767, minValue: -32768 }).
• schemas.int32 ... Equivalent to schemas.number({ intOnly: true, maxValue: 2147483647, minValue: -2147483648 }).
• schemas.uint8 ... Equivalent to schemas.number({ intOnly: true, maxValue: 255, minValue: 0 }).
• schemas.uint16 ... Equivalent to schemas.number({ intOnly: true, maxValue: 65535, minValue: 0 }).
• schemas.uint32 ... Equivalent to schemas.number({ intOnly: true, maxValue: 4294967295, minValue: 0 }).

➡️ class ValidationError

The Error class for validation errors.

➡️ object DefaultMessage

The default error messages.

➡️ type Message

The interface to define your own error messages.

See src/message/default-message.ts for example.

➡️ type Schema

The types of schemas.

See src/schema-types.ts for details.

➡️ type TypeOf<T>

The types for calculating the value type of schemas.

See src/real-types.ts for details.

➡️ type Validate<T>

The type of validation functions.

type Validate<T extends Schema> = (
  name: string,
  value: any
) => asserts value is TypeOf<T>;

📰 Changelog

See GitHub Releases.

🍻 Contributing

Welcome contributing!

Please use GitHub's Issues/PRs.

Development Tools

• npm test runs tests and measures coverage.
• npm run build compiles source code to index.mjs, index.js, index.mjs.map, index.js.map, and index.d.ts.
• npm run clean removes the temporary files which are created by npm test and npm run build.
• npm run format runs Prettier.
• npm run lint runs ESLint.
• npm version <patch|minor|major> makes a new release.