Loaded but not executed

System.register("common", [], function(exports_1, context_1) {
    "use strict";
    var __moduleName = context_1 && context_1.id;
    function helloWorld() {
        return "Hello World";
    }
    exports_1("helloWorld", helloWorld);
    return {
        setters:[],
        execute: function() {
        }
    }
});
System.register("app", ["common"], function(exports_2, context_2) {
    "use strict";
    var __moduleName = context_2 && context_2.id;
    var C;
    return {
        setters:[
            function (C_1) {
                C = C_1;
            }],
        execute: function() {
            alert(C.helloWorld());
        }
    }
});