This is the first step in an Dependency Injection Framework in Javascript:

Now updated to show passing on the registry.

This still needs work.  It is OK for the Registry to be a global, but the resolution of an component should be scoped….Like I said, a first step.

#!/usr/bin/rhino

var Registry = {

    factories : {},
    instances : {},

    register:  function(name,factory){

        this.factories[name] = factory;

        this.__defineGetter__(name, function() {

            if (!this.instances[name]){
                this.instances[name] = this.factories[name](this);
            }

            return this.instances[name];
        });
    }
}

Registry.register("teststring",function(){
    return "Injected";
});

Registry.register("testobj",function(registry){
    var that = {};
    that.string = registry.teststring;
    that.execute = function(){
        print(that.string);
    }
    return that;
});

Registry.testobj.execute();

Updated: This version would keep a separate instance variable per “request”

#!/usr/bin/rhino

var Registry = {

    factories : {},
    keys: [],
    register:  function(name,factory){
        this.factories[name] = factory;
        this.keys.push(name);
    },

    define_getter: function(scope,key){
        var facts = this.factories;
        scope.__defineGetter__(key, function() {
            var x = key;
            if (!scope.instances[x]){
                scope.instances[x] = facts[x](scope);
            }
            return scope.instances[key];
        });
    },

    request_scope: function(){
        var scope = {};
        scope.instances = {};
        var facts = this.factories;
        for (var i = 0; i < this.keys.length; i +=1){
            this.define_getter(scope,this.keys[i]);
        }
        return scope;
    }
}


Registry.register("teststring",function(scope){
    return "Injected";
});

Registry.register("testobj",function(scope){
    var that = {};
    that.string = scope.teststring;
    that.execute = function(){
        print("executing " + that.string);
    }
    return that;
});


var scope =  Registry.request_scope();

var test_string = scope.teststring;
var test_obj = scope.testobj;
test_obj.execute();