Dependency injection in JavaScript

bar.js

/* A basic implementation of bar */
define(function () {
  return {
    plop: function () { alert('bar implementation'); }
  }
});

baz.js

/* An alternative implementation of bar */
define(function () {
  return {
    plop: function () { alert('baz implementation'); }
  }
});

foo.js

/*
 * foo is a module that depends on a bar module.
 * Note that the dependency is modeled as a parameter of the function returned by the module definition.
 */
define(function () {
  return function (bar) {
    return bar.plop()
  }
});

usage.js

/* The end-user wires dependencies */
require(['foo', 'baz'], function (fooProvider, bazProvider) {
  var baz = bazProvider();
  var foo = fooProvider(baz);
})

Ok, indeed if several implementations have a different API the problem is not the same :)