idd v0.1.1

idd

A dependency injection system with destructuring. Combines a common pattern of using a single destructuring argument to avoid confusing the order of arguments to high-parity functions, possibly with many optional parameters.

Getting Started

To install the dependency injection system, use npm install

npm install --save idd

Then, from other peer directories, you can require the files as properties on the directory's default export

lib/config.js

export default function () {
	return {
		language: 'ru-ru',
		level: 'info'
	};
};

lib/greeter.js

export default ({config, Logger}) => {
	const logger = new Logger();
	return {
		greet: () => {
			if (config.language === 'en-us') {
				logger.log('Hello World!');
			} else if (config.language === 'ru-ru') {
				logger.log('Привет, мир!');
			} else {
				logger.error('unsupported language ' + config.language);
			}
		}
	};
};

lib/Logger.js

import chalk from 'chalk';

export default () => class Logger {
	constructor() {
		this.level = process.env.LEVEL;
	}
	log(msg) {
		if (this.level !== 'quiet') {
			console.log(msg);
		}
	}
	error(msg) {
		if (this.level !== 'quiet' && this.level !== 'silent') {
			chalk.red(msg);
		}
	}
};

index.js

import path from 'path';
import idd from '../../../..';

const {greeter} = idd(path.join(__dirname, 'lib'));

greeter.greet();

Then the output would be 'Hello World!'. If you were to change config to be instead

export default function() {
	language: 'ru-ru',
	level: 'error'
}

Then the output would be 'Привет, мир!'.

Testing

A good dependency injection system should make unit testing easy. To mock out your dependencies, just provide an optional third option with the mocks

import {sinon} from 'sinon';
import idd from 'idd';
import test from 'ava';

test('Greet was called', t => {
	const greet = sinon.spy();
	const config = { greeting: 'Hello World!'};
	const {greeter} = idd('./lib', { config, greet });

	greeter.greet();

	t.true(greet.calledOnce);
});