Javascript IoC / DI frameworks [closed]

Question

For strongly typed static languages like Java, IoC / DI frameworks / toolkits are invaluable to decouple the complex systems thus make the sub-components unit testable and their composition fluently.

Most of us cite that Javascript as loosely typed dynamic language already offers the major benefits of IoC / DI in spirit, while some insist that higher level abstraction / implementation should be in place.

For the latter, what are those common IoC / DI implementations in Javascript realm?

Answer 1

Please have a look into wire.js. This is my choice and it works great.

The main features are:

• Simple, declarative dependency injection
• A flexible, non-invasive connection infrastructure
• Application lifecycle management
• Powerful core tools and plugin architecture for integrating popular frameworks and existing code.
• Support for both browser and server environments

Also please check some alternatives npm modules for DI

Answer 2

Javascript's Duck-Typing allows us to easily mock dependencies.

Here is a quick example of how you could do this:

We have a simple function which represents an item being added to the database. DB is a dependency which we will want to mock.

function SaveItem(item){

    var db = new DB();

    db.insert(item);

};

If we change the DB dependency to be a parameter, then we can inject whatever we want. When the function is called it checks to see if the dataStore parameter exists. When the item exists the value is assigned to db. When dataStore is null or undefined, then a new DB object is created instead. This allows you to inject in your dependency with the confidence that db will always have a value.

function SaveItem(item, dataStore){

    var db = dataStore || new DB();

    db.insert(item);

};

Now we can mock our dependency like so:

function mockDb(){

    return{
        insert: function(){ 
            assert(true);  
        }
    }

};

And to bring it all together in a test:

function SaveItemShouldCallInsertOnDb = function(){

    var testDb = new mockDb();
    var someTestItem = { name: "test item" };

    SaveItem(someTestItem, testDb);
};