jdpedrie/DI.js

## DI.js
var di = function() {
  var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;
  var ARGUMENT_NAMES = /([^\s,]+)/g;

  var deps = {};

  var getParamNames = function(func) {
    var fnStr = func.toString().replace(STRIP_COMMENTS, '');
    var result = fnStr.slice(fnStr.indexOf('(')+1, fnStr.indexOf(')')).match(ARGUMENT_NAMES);
    if(result === null) {
      result = [];
    }

    return result;
  };

  var invoke = function(dep) {
    var params = [];

    getParamNames(dep).forEach(function(paramName) {
      params.push(this.get(paramName));
    }, this);

    return dep.apply(window, params);
  };

  function diError(message) {
    this.name = 'diError';
    this.message = message;
  }
  diError.prototype = new Error();
  diError.prototype.constructor = diError;

  return {
    /**
     * Add a service to the dependency injector.
     * value is usually a function. If value is anything other than a function, invoke MUST be false.
     * If invoke is true or undefined, value is invoked before being injected.
     * @param string key
     * @param mixed  value
     * @param bool   invoke
     */
    add: function(key, value, invoke) {
      invoke = (typeof invoke === 'undefined') ? true : invoke;

      if (!!invoke && typeof value !== 'function') {
        throw new diError('value is not a function');
      }

      deps[key] = {
        value: value,
        invoke: !!invoke
      };
    },

    /**
     * Add a value to the dependency injector.
     * Essentially a shortcut for add('key', 'val', false);
     * These are never invokable.
     * @param string key
     * @param mixed  value
     */
    value: function(key, value) {
      return this.add(key, value, false);
    },

    /**
     * Fetch a value from the dependency injector.
     * If it is invokable, it will try to resolve any dependencies the value asks for.
     * @param string key
     */
    get: function(key) {
      if (typeof deps[key] === 'undefined') {
        throw new diError('Dependency `'+ key +'` is not defined');
      }

      var dep = deps[key];

      if (dep.invoke && typeof dep.value !== 'function') {
        throw new diError('Cannot invoke dependency because dependency is not a function!');
      }

      return (dep.invoke) ? invoke.call(this, dep.value) : dep.value;
    }
  };
};

## index.html
<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <title>Dependency Injection Example</title>
</head>
<body>
  <h1 id="greeting"></h1>

  <script src="di.js"></script>
  <script>
    var app = di();
    app.add('myCtrl', function(DOMGuy, greeting) {
      DOMGuy.updateElementValue('greeting', greeting);
    });

    app.add('DOMGuy', function() {
      return {
        updateElementValue: function(id, value) {
          document.getElementById(id).innerHTML = value;
        }
      };
    });

    app.value('greeting', 'Hello Worldzzz!', false);

    app.get('myCtrl');
  </script>

</body>
</html>
	var di = function() {
	var STRIP_COMMENTS = /((\/\/.$)\|(\/\[\s\S]?\\/))/mg;
	var ARGUMENT_NAMES = /([^\s,]+)/g;

	var deps = {};

	var getParamNames = function(func) {
	var fnStr = func.toString().replace(STRIP_COMMENTS, '');
	var result = fnStr.slice(fnStr.indexOf('(')+1, fnStr.indexOf(')')).match(ARGUMENT_NAMES);
	if(result === null) {
	result = [];
	}

	return result;
	};

	var invoke = function(dep) {
	var params = [];

	getParamNames(dep).forEach(function(paramName) {
	params.push(this.get(paramName));
	}, this);

	return dep.apply(window, params);
	};

	function diError(message) {
	this.name = 'diError';
	this.message = message;
	}
	diError.prototype = new Error();
	diError.prototype.constructor = diError;

	return {
	/**
	* Add a service to the dependency injector.
	* value is usually a function. If value is anything other than a function, invoke MUST be false.
	* If invoke is true or undefined, value is invoked before being injected.
	* @param string key
	* @param mixed value
	* @param bool invoke
	*/
	add: function(key, value, invoke) {
	invoke = (typeof invoke === 'undefined') ? true : invoke;

	if (!!invoke && typeof value !== 'function') {
	throw new diError('value is not a function');
	}

	deps[key] = {
	value: value,
	invoke: !!invoke
	};
	},

	/**
	* Add a value to the dependency injector.
	* Essentially a shortcut for add('key', 'val', false);
	* These are never invokable.
	* @param string key
	* @param mixed value
	*/
	value: function(key, value) {
	return this.add(key, value, false);
	},

	/**
	* Fetch a value from the dependency injector.
	* If it is invokable, it will try to resolve any dependencies the value asks for.
	* @param string key
	*/
	get: function(key) {
	if (typeof deps[key] === 'undefined') {
	throw new diError('Dependency `'+ key +'` is not defined');
	}

	var dep = deps[key];

	if (dep.invoke && typeof dep.value !== 'function') {
	throw new diError('Cannot invoke dependency because dependency is not a function!');
	}

	return (dep.invoke) ? invoke.call(this, dep.value) : dep.value;
	}
	};
	};
	<!doctype html>
	<html lang="en">
	<head>
	<meta charset="UTF-8" />
	<title>Dependency Injection Example</title>
	</head>
	<body>
	<h1 id="greeting"></h1>

	<script src="di.js"></script>
	<script>
	var app = di();
	app.add('myCtrl', function(DOMGuy, greeting) {
	DOMGuy.updateElementValue('greeting', greeting);
	});

	app.add('DOMGuy', function() {
	return {
	updateElementValue: function(id, value) {
	document.getElementById(id).innerHTML = value;
	}
	};
	});

	app.value('greeting', 'Hello Worldzzz!', false);

	app.get('myCtrl');
	</script>

	</body>
	</html>