Type checking and DDD for JavaScript
npm install tcomb
!npm downloads
> "Si vis pacem, para bellum" - (Vegetius 5th century)
tcomb is a library for Node.js and the browser which allows you to check the types of JavaScript values at runtime with a simple and concise syntax. It's great for Domain Driven Design and for adding safety to your internal code.
You may want to check out io-ts
tcomb is supposed to be used in development and is disabled in production.
If you want type checks in production you may use
- tcomb-validation
- io-ts
``sh`
npm install tcomb --save
Code example
A type-checked function:
`js
import t from 'tcomb';
function sum(a, b) {
t.Number(a);
t.Number(b);
return a + b;
}
sum(1, 's'); // throws '[tcomb] Invalid value "s" supplied to Number'
// using babel-plugin-tcomb
function sum(a: number, b: number) {
return a + b;
}
`
A user defined type:
`js`
const Integer = t.refinement(t.Number, (n) => n % 1 === 0, 'Integer');
A type-checked class:
`js
const Person = t.struct({
name: t.String, // required string
surname: t.maybe(t.String), // optional string
age: t.Integer, // required integer
tags: t.list(t.String) // a list of strings
}, 'Person');
// methods are defined as usual
Person.prototype.getFullName = function () {
return ${this.name} ${this.surname};
};
const person = Person({
surname: 'Canti'
}); // throws '[tcomb] Invalid value undefined supplied to Person/name: String'
`
Chrome DevTools:
- API
- A little guide to runtime type checking and runtime type introspection (Work in progress)
Lightweight
3KB gzipped, no dependencies.
Type safety
All models defined with tcomb are type-checked.
Note. Instances are not boxed, this means that tcomb works great with lodash, Ramda, etc. And you can of course use them as props to React components.
Based on set theory
- Blog post: JavaScript, Types and Sets - Part I
- Blog post: JavaScript, Types and Sets - Part II
Domain Driven Design
Write complex domain models in a breeze and with a small code footprint. Supported types / combinators:
* user defined types
* structs
* lists
* enums
* refinements
* unions
* intersections
* the option type
* tuples
* dictionaries
* functions
* recursive and mutually recursive types
* interfaces
Immutability and immutability helpers
Instances are immutable using Object.freeze. This means you can use standard JavaScript objects and arrays. You don't have to change how you normally code. You can update an immutable instance with the provided update(instance, spec) function:
`js`
const person2 = Person.update(person, {
name: { $set: 'Guido' }
});
where spec is an object containing commands. The following commands are compatible with the Facebook Immutability Helpers:
* $push
*
*
*
*
*
See Updating immutable instances for details.
Speed
Object.freeze calls and asserts are executed only in development and stripped out in production (using process.env.NODE_ENV !== 'production' tests).
Runtime type introspection
All models are inspectable at runtime. You can read and reuse the information stored in your types (in the meta static member). See The meta object in the docs for details.
Libraries exploiting tcomb's RTI:
- tcomb-validation
- tcomb-form
- Blog post: JSON API Validation In Node.js
Easy JSON serialization / deserialization
Encodes / decodes your domain models to / from JSON for free.
- Blog post: JSON Deserialization Into An Object Model
Debugging with Chrome DevTools
You can customize the behavior when an assert fails leveraging the power of Chrome DevTools.
`js
// use the default...
t.fail = function fail(message) {
throw new TypeError('[tcomb] ' + message); // set "Pause on exceptions" on the "Sources" panel for a great DX
};
// .. or define your own behavior
t.fail = function fail(message) {
console.error(message);
};
`
Pattern matching
`js
const result = t.match(1,
t.String, () => 'a string',
t.Number, () => 'a number'
);
console.log(result); // => 'a number'
`
Babel plugin
Using babel-plugin-tcomb you can also write (Flow compatible) type annotations:
`js`
function sum(a: number, b: number): number {
return a + b;
}
TypeScript definition file
- Giulio Canti maintainer
- Becky Conning func combinator ideas and documentationdeclare
- Andrea Lattuada combinator
`sh`
git clone git@github.com:gcanti/tcomb.git
cd tcomb
npm install
npm run dist
Will output 2 files:
- dist/tcomb.js (development)dist/tcomb.min.js
- (production) Object.freeze` calls and asserts stripped out
* tcomb-doc Documentation tool for tcomb
* tcomb-validation Validation library based on type combinators
* tcomb-json-schema Transforms a JSON Schema to a tcomb type
* reactuate React/Redux stack (not a boilerplate kit)
* tcomb-react Alternative syntax for PropTypes
* mongorito-tcomb Bring schema validation to Mongorito thanks to tcomb
* tcomb-form Forms library for react
* tcomb-form-types Adds Types/Validations to tcomb-form
* tcomb-form-native Forms library for react-native
* tcomb-generate Generates random data by tcomb type for property-based testing
* tcomb-additional-types Provides additional predefined types for your existing tcomb setup
* tcomb-builder An immutable syntax for defining tcomb types and forms
* typed-immutable
* immu
* immutable
* mori
* seamless-immutable
* deep-freeze
* freezer
* icedam
* ObjectModel
* rfx
The MIT License (MIT)