flacon 💉

flacon is a dependency injection container with a clean and tiny API that helps you to test your components individually. .5k minified & gzipped.

• Flexible – It does not care about what a module factory returns.
• Unopinionated – It does not interfere with require calls.
• Simple – Less than 100 lines of code.

Installing

npm install flacon

Introduction

Imagine you have a service foo.js.

module.exports = {
	value: () => 'foo'
}

Now you want another service bar.js that uses foo.js.

const foo = require('./foo')

module.exports = {
	value: () => foo.value() + 'bar'
}

This looks all good. But when testing bar.js, mocking foo.js is really difficult because it is a private dependency. flacon, on the other hand, forces you to explicitly declare all dependencies, making it easy to mock them.

create a container

First, we create a new container in container.js. On a container, you can publish and load modules.

const Flacon = require('flacon')
module.exports = new Flacon()

publish modules

Let's start with foo.js. We call the publish method with an id and a factory function.

const container = require('./container');

container.publish('foo', () => ({
	value: () => 'foo'
}))

Moving on to bar.js, we define foo as a dependency. The result of foo's factory will be passed into bar's factory.

const container = require('./container')

const factory = (foo) => ({
	value: () => foo.value() + 'bar'
})
factory.deps = ['foo']
container.publish('bar', factory)

load modules

By simply calling the container with a module id, you will get the return value of the factory function.

const container = require('./container')

const bar = container('bar')
bar.value() // -> 'foobar'

mock dependencies

During testing, we can easily manipulate or mock a dependency. This will load every mocked module without caching.

const container = require('./container')

const bar = container('bar', {
	foo: (foo) => ({
		value: () => 'baz'
	})
})
bar.value() // -> 'bazbar'

Note: In a mock function, make sure to never manipulate given module, always return a new one!

flush

To force flacon to call a module's factory again, use flush.

container.load('foo')  // factory creates module
container.flush('foo')
container.load('foo')  // factory creates module again

API

flacon(id, [mocks])

Loads a module by id. Caches and returns the module.

mocks is an object of mocking functions by id. Mocked dependencies will not be cached.

• id: The identifier, unique to the container.
• mocks: A map of callbacks, mapped by module id. The return value of each callback will be the mock.

flacon.publish(id, factory)

Registers a module by id. Reads the module's dependencies from factory.deps. Returns the module's factory.

• id: The identifier, unique to the container.
• factory: A function, taking the dependencies, that returns the module.

flacon.flush()

Removes a module from the cache. Returns the container.

• id: The identifier, unique to the container.

Contributing

If you have a question, found a bug or want to propose a feature, have a look at the issues page.