Introduction

Do you ever feel like you have to jump through hoops to get something done? The same can be said for coding. Many modern web-developers are familiar with the proxy design pattern. It simplifies complex tasks, making coding more efficient.

The proxy pattern is basically a way to dictate how other objects are accessed. If you are looking for an easy way to keep control of the data you're working with, the proxy design pattern is an excellent choice. This article will teach you how to implement this design pattern in Javascript.

What is the Proxy Design Pattern?

The proxy design pattern is a structural programming scheme that acts as a wrapper around another object. It allows access to complex objects, enhancing flexibility. It is designed to hide implementation details and provide a simpler structure for code. It can also be used to manipulate data or restrict access to certain parts of an application.

Why Use the Proxy Design Pattern?

Using the proxy design pattern provides a few key advantages;

• It simplifies the structure of code.
• It improves the performance of the code by reducing repetitions,
• It provides a layer of security to restrict access to certain parts of the code.
• It can be used to create flexible API’s.

Where Is The Proxy Design Pattern Used?

The proxy design pattern is widely used in web development. It is used to simplify client/server interactions, API queries, or other data-modeling needs. It can also be used in libraries, frameworks, and even in databases.

How Does the Proxy Design Pattern Work?

At its simplest, a proxy is an intermediary object that takes the place of another object. It is usually implemented as a function that takes the input and passes it on to the underlying object.

The proxy design pattern can be implemented in a variety of ways depending on the specific task needed. The most common implementations are to provide caching, logging, and validation.

Use Cases

1. Caching

Caching is a popular use-case for proxies, as it enhances the performance of code when working with frequently used objects.

For example, consider the following piece of code:

const getRequest = (url) => {
  fetch(url)
    .then((response) => response.json())
    .then((data) => console.log(data));
}

To cache the result of the request, we can use a proxy to provide a layer of abstraction over the fetch() function. This way, we can store the response of the request, so it doesn't have to be made again if the same request is called.

const getCachedRequest = (proxy, url) => {
  // check if URL result is already cached
  const cachedResult = proxy.getCachedResult(url);
  if (cachedResult) {
    return cachedResult;
  }
  // if not, make the request and cache the result
  return fetch(url)
    .then((response) => cache.addCachedResult(url, response.json()) )
    .then((data) => console.log(data));
}

The code for the proxy looks something like this:

const proxy = {
  cache: {},
  getCachedResult: (url) => proxy.cache[url],
  addCachedResult: (url, result) => proxy.cache[url] = result,
};

2. Logging

Logging is a great use-case for proxy design. It provides a layer of abstraction over logging tasks, allowing us to easily track errors, warnings, and general information about what is happening within the application.

For example, consider the following code:

const getRequest = (url) => {
  fetch(url)
    .then((response) => response.json())
    .then((data) => console.log(data));
}

To log the request, we can use a proxy to provide a layer of abstraction over the fetch() function. This way, we can store the request URL and the response data, so we can easily see when requests are made and what they returned.

const getRequestLogged = (proxy, url) => {
  return fetch(url)
    .then((response) => proxy.logRequest(url, response.json()) )
    .then((data) => console.log(data));
}

The code for the proxy looks something like this:

const proxy = {
  log: [],
  logRequest: (url, result) => {
    proxy.log.push({
      url: url,
      result: result
    })
  }
};

3. Validation

The proxy design pattern is also great for validation. It can be used to prevent changes to an object that invalidate the data.

For example, consider a basic model object with a few fields and a function to set them.

const model = {
  name: '',
  age: 0,
  setName(name) {
    model.name = name;
  },
  setAge(age) {
    model.age = age;
  }
}

To prevent mistakes, we can use a proxy to validate the data before it is set in the model.

const validateSetName = (proxy, name) => {
  if (proxy.isValidName(name)) {
    model.setName(name);
  } else {
    console.log('Invalid name');
  }
}

The code for the proxy looks something like this:

const proxy = {
  isValidName: (name) => name.length > 2,
};

Conclusion

As you can see, the proxy design pattern is a great way to structure code and improve its performance by providing layers of abstraction and validation. It is especially useful when dealing with complex tasks and data entry. We hope this article has provided you with the information necessary to start using the proxy design pattern in your own projects.

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