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    Javascript Dependency Injection library

    DI makes classes accessible by a contract. Instances are created when requested and dependencies are injected into the constructor, facilitating lazy initialization and loose coupling between classes.

    As an example, consider a User and Persitance classes:

    function WebSql(name, fieldList)  {
        this.persist = function (obj) {
            console.log('WebSQL will persist:');
            fieldList.forEach(function (field) {
                console.log('    ' + field + ': ' + obj[field]);
    function IndexDB(name, fieldList)  {
        this.persist = function (obj) {
            console.log('IndexDB will persist:');
            fieldList.forEach(function (field) {
                console.log('    ' + field + ': ' + obj[field]);
    function User(email, passwd, storage, role) {    // the `storoge` parameter holds an instance = email;
        this.passwd = passwd;
        this.role = role;
    = function () {

    With these classes in our pocket its time to setup the relations between them. The function that does this has the following signature

     function (<contract name>, 
               <class reference>, 
               [optional list of constructor arguments], 
               {optional configuration object} ) 

    Or just in code:

    var di = new DI();
    di.register('user', User, [null, 'welcome', 'websql', 'nobody']);
    di.register('websql', WebSql, ['userTable', ['email','passwd', 'role']], {singleton: true});
    di.register('indexdb', IndexDB, ['userTable', ['email','passwd', 'role']], {singleton: true});

    Note that the provied constructor arguments are default values or contract names. From now it is easy to create instances:

    var user1 = di.getInstance('user', ['']),
            -> email: '', passwd: 'welcome', storage : WebSQL instance, role: 'nobody'
        user2 = di.getInstance('user', ['', 'newSecret']); // define a new password
            -> email: '', passwd: 'newSecret', storage : WebSQL instance, role: 'nobody'
    if (user1 instanceof User) { /* user1 is an instance of User!! */ }

    But it is also possible to use IndexDB as the persistance class:

    var user = di.getInstance('user', ['', null, 'indexdb']),               // The password is set to null too!
            -> email: '', passwd: null, storage : IndexDB instance, role: 'nobody'
        root = di.getInstance('user', ['', undefined, 'indexdb', 'admin']); 
            -> email: '', passwd: 'welcome', storage : IndexDB instance, role: 'admin'

    Checkout more detailed the documentation here

    Gulp tasks

    Install the dependencies as follows

    $> npm install

    To minify the library

    $> gulp

    To run the tests

    $> gulp test


    $> bower install javascript-dependency-injection


    npm i javascript-dependency-injection

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    • jeanluca