node-dough -- Simple dependency injection for node.js

node-dough is a simple dependency injection library for node.js. It maps string keys to providers, which are simply asynchronous functions. For instance:

var dough = require("dough");

var injector = dough.newInjector();
injector.bind("username").toProvider(function(callback) {
    callback(null, "Bob");
});
injector.get("username", function(err, username) {
    // username === "Bob"
});

The dependencies of a provider can be specified by passing them as additional arguments to toProvider:

injector.bind("user").toProvider(function(callback) {
    callback(null, {name: "Bob"});
});
injector.bind("username").toProvider(function(user, callback) {
    callback(null, user.name);
}, "user");
injector.get("username", function(err, username) {
    // username === "Bob"
});

Although they all ultimately delegate to using toProvider, bindings can be specified with other methods:

// Binding to constants
injector.bind("username").toConstant("Bob");
injector.get("username", function(err, username) {
    // username === "Bob"
});

// Binding to synchronous functions
injector.bind("username").toSyncProvider(function() {
    return "Bob";
});
injector.get("username", function(err, username) {
    // username === "Bob"
});