The two child methods returned have access to the scope created by createFactories, and thus the logger that was passed in. It enables the logger to be encapsulated within createFactories' scope, which will remain after the function has been executed. However, we'll still have access to the logger reference through emailFactory and smsFactory.

Combining Closures and Dependency Injection

We'll create a factory function that accepts a logger and a starting value for a counter. It will return an object containing a decrementing counter function (minus) and a logging factory (createFactories), demonstrating both closures and dependency injection.

• The CounterAndLoggerFactory function encapsulates both a decrementing counter (using a closure) and a set of factories that use a logger (demonstrating dependency injection).
• The counter variable is private and can only be accessed through the minus function.
• The createFactories function returns two factory functions that utilize the injected logger.
• The returned object allows access to both the minus function and the createFactories function, enabling both decrementing counter functionality and logging functionality.

By combining closures and dependency injection in this way, the code snippet showcases the versatility and power of these concepts in JavaScript, allowing for modular, maintainable, and flexible design.

Complexity of Final Solution

O(1) constant time & space complexity, this is a knowledge question!

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emailSender("John!"); // Logs: Hello, John!

function CounterAndLoggerFactory(startValue, logger) {

  var counter = startValue;

​

  var minus = function () {

    counter -= 1;

    return counter;

  };

​

  function createFactories() {

    return {

      emailFactory: function(greeting) {

        return function(greet) {

          logger(greeting + greet);

        };

      },

      smsFactory: function(text) {

        return function(text) { logger(text); };

      }

    };

  }

​

  return {

    minus: minus,

    createFactories: createFactories

  };

}

​

// Usage Example:

var logger = console.log;