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Node.js Design Patterns

Implementation of Command Pattern

Explore how to implement the Command pattern in Node.js by creating commands that encapsulate operations with run, undo, and serialize methods. Learn to control and schedule tasks, support undo functionality, and serialize commands for remote execution. This lesson guides you through both simple and complex command implementations, helping you understand when to use the pattern effectively for asynchronous programming.

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Now, we’re going to explore a couple of different implementations of the Command pattern in more detail, just to get an idea of its scope.

The Task pattern

We can start off with the most basic and trivial implementation of the Command pattern: the Task pattern. The easiest way in JavaScript to create an object representing an invocation is, of course, by creating a closure around a function definition or a bound function. 

function createTask(target, ...args) {
  return () => {
    target(...args)
  }
}

This is (mostly) equivalent to doing the following:

  const task = target.bind(null, ...args)

This shouldn’t look new at all. This technique allows us to use a separate component to control and schedule the execution of our tasks, which is essentially equivalent to the invoker of the Command pattern.

A more complex command

Let’s now work on a more articulated example leveraging the Command pattern. This time, we want to support undo and serialization. Let’s start ...