JavaScript Dependency Injection

A simple and lightweight JavaScript library for Dependency Injection/Inversion of Control (DI/IoC) with no dependencies.

Suitable for Node and browsers.

Written strictly in ES2015; Webpack/Babel/... should be managed by consumers.

There are other libraries that are more powerful but also are more complex and with bigger goals (such as InversifyJS). We focus on simplicity and cleanest API possible.

Getting started

Install with npm:

npm install --save @csgis/di

or yarn:

yarn add @csgis/di

And use it in your module:

import di from '@csgis/di';

class Map {
  addLayer(opts) {
    // ...
  }
}

class OLMap extends Map {
  addLayer(opts) {
    console.log('OLMap adding layer...');
    // ...
  }
}

di.bind(Map, OLMap);

var map = di.get(Map);
map.addLayer({
  // ...
});

You might need to bundle it properly for running, for example, in Node:

yarn add -D webpack
node_modules/.bin/webpack --target node index.js bundle.js
node bundle.js

Examples

Binding literal values

di.bind('value', 42);

Binding singletons

class Map {
  addLayer(opts) {}
}
class OLMap extends Map {
  addLayer(opts) {
    // ...
  }
}

di.bind(Map, new OLMap());

Binding classes

class Map {
  addLayer(opts) {}
}
class OLMap extends Map {
  addLayer(opts) {
    /// ...
  }
}

di.bind(Map, OLMap);

Binding classes with injected members:

class Renderer {
  render() {}
}
class WebGLRenderer extends Renderer {
  render() {
    // ...
  }
}
class Map {
  addLayer(opts) {}
}
class OLMap extends Map {
  constructor() {
    super();
    this.$inject = {
      renderer: Renderer
    };
  }

  addLayer(opts) {
    // ...
    this.renderer.render();
  }
}


di.bind(Renderer, new WebGLRenderer());
di.bind(Map, OLMap);
di
.get(Map) // here the new OLMap instance has the renderer member injected with the WebGLRenderer instance.
.addLayer({
  // ...
}); // this calls render in injected WebGLRenderer as part of the addLayer method in OLMap.

Injecting objects

class Map {
  addLayer(opts) {}
}
class OLMap extends Map {
  addLayer(opts) {
    // ...
  }
}

di.bind(Map, new OLMap());

var obj = {
  $inject = {
    mymap: Map
  }
}
di.inject(obj);

obj.mymap.addLayer({
  // ...
});

Removing all bindings

di.reset();

API

bind(service, obj)

Binds a literal, object or class to a service.

• service (string or class): If class, it checks that obj is either a subclass or an instance of service.

• obj: It can be anything when service is a string.

  It must be a subclass or an instance of service when service is a class. If it's an instance, get will return the exact instance; if it's a class, it will return a new instance by calling the constructor with no params.

Throws DIError.

inject(obj)

Injects an existing object based on its $inject property.

• obj An object with an $inject property. $inject is an object whose keys are property names and values are services.

Throws DIError.

get(service)

Gets a bound literal or object.

• service: A string or class previously used with the bind function.

Throws DIError.

reset()

Removes all bindings.

DIError

Generic error for injecting problems. Extends Error. Can be imported by:

import { DIError } from '@csgis/di';