Learn Express, Gatsby and Python

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

express

Learn about security headers by adding them to an Express app in a step-by-step guide.

We're going to cover:
- default request headers
- what are security headers
- why security headers are important
- how to add security headers using Helmet
- how to configure the newly added security headers

Add Security Headers to an Express app

Python is a widely used dynamically typed programming language. It allows for many different programming paradigms including object-oriented, imperative, functional programming, and procedural styles.

python

To take the user input in Python you use a built-in method input(). The data type of the user input is string. Later based on the use case the data type of the user input can be changed to a different data type based on the requirement.

 Example:

1. 
```
>> a = input("Enter your birthday date ")
>> 31
>> a
>> '31' 
```

2. 
```
>> b = input("Enter List of numbers: ")
>> [1, 2, 3, 4]
>> b
>>  '[1, 2, 3, 4]'
```

NOTE: While creating the example Python interpreter is used which is why the program waits for the user to input. And, once the user enters the input then prompts the user to enter the next line of code.


Use built-in method input() to take User Input in Python

Use the equality operator to compare the values of the objects. Identity operator is used to verifying that objects are equal but are not referring to the same object in memory. 

Use cases where identity operator is used are:
- to test if the object is None
- to test if the object is of a particular type or not

There may be use cases where the output returned by both the operators is the same. But, in your program, you have used the identity operator instead of the equality operator. 

To avoid such mistakes it is important to understand the difference between identity and equality operator.


Difference between Equality Operator and Identity Operator in Python

The identity operator is used for checking whether the object is of the mentioned type.

Example:

```
>> a = "Hello World!"
>> type(a) is str
>> True
```
The result returned in the above case is true because the type of object is str. 

Identity operator is also used to compare the object with None. 

Example:

```
>> a = None
>> a is None
>> print(a)
>> True
```

Internally, the identity operator compares the memory address of the objects. Built-in `id()` method returns a unique number i.e address of the object in memory. If the address of both the objects in memory is the same identity operator returns the result as True.

Example:

```
>> a = 10
>> b = 10
>> a is b
>> True
>> id(a)
>> 916744
>> id(b)
>> 916744
```

The above code snippet tells us that value of both the objects is the same and variables `a` and `b` are referring to the same object in memory. 



Identity Operator in Python

Variable names in Python can be of any length. Variables names can have alphabets [A-Z][a-z], digits [0-9] and underscores. A variable name starting with a digit is an invalid variable name. 

Variable Names in Python

Built-in id() method determines the memory address of the object in Python. Knowing this concept will help you in understanding what happens under the hood when you use identity operator (is and not is). 

Use Built-in id() Method to Determine the Memory Address of the Object

While solving real-life use cases through programming and also while testing your code you will come across scenarios where you have to compare the value of different objects. And, then to solve the problem you can use the equality operator.

Use Equality Operator to Compare the Value of Objects in Python

We'll create our client-server using the `express` and `cors` packages

Express will be used to create our HTTP application. We'll need it to post to our endpoints and listen to our port.

We need the `cors` package to make cross-origin requests since the front-end will be a different origin than the server.

Create an OAuth Client-Server for code/token exchange

 Every developer who has attempted to demystify OAuth 2.0 must be presented with mind-bugging complicated flow diagrams. It becomes worse when you try to understand all the terminologies of OAuth 2.0 and Open ID protocols.

There is no getting around the OAuth 2.0 flow being complicated with back and forth between your browser, the service you are authenticating with, and the application you want to access. 

This course gets straight to the point without any application code distracting you from the core takeaway -- You will learn how to authenticate and authorize yourself using GitHub as your Auth Server.

We'll first cover the OAuth 2.0 flow for authentication and then integrate the Open ID protocol for authorization.

[**LIVE EVENT**: Register here for a live webinar with Christian on OAuth.](https://egghead.zoom.us/webinar/register/WN_Sxy1FEcoTea8UA6F7EDzLw) Bring any questions you have from taking this course!

JSON Web Tokens are an open, industry standard RFC 7519 method for representing claims securely between two parties.

Add Github Login to Your Web App with OAuth 2.0

React is one of the web’s most popular frameworks for building JavaScript applications. 

If you know what you’re doing, React can drastically simplify how you build, use, and maintain code.

Whether you’re a React newbie or you’re ready for advanced techniques, you can level-up with egghead. Explore our in-depth courses, lessons, and community resources to build more powerful applications and crack open your career.

react

Role-Based Access Control (RBAC) is the idea of grouping permissions together by a role. Users are assigned a role through the Auth0 dashboard the corresponding permissions are placed on the user's access token (JWT) after authenticating. That access token can be extracted by an Auth0 SDK (this video uses JavaScipt/ ReactJS) and sent to a custom server. 

Server Side logic (this video is based on NodeJS and ExpressJS), can then check for specific permissions and then allow or reject certain resources. 

-------------

Starting point- https://github.com/twclark0/roles-scopes-node-auth0/tree/roles-beginning

Ending point- https://github.com/twclark0/roles-scopes-node-auth0/tree/roles-final

Role Based Auth in NodeJS with ExpressJS and Auth0

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

Nx is not only capable of scaffolding frontend projects, but it also supports a lot of backend setups. In this specific lesson, we're going to explore the setup we previously generated, specifically inspecting how passing `--frontentProject` to the Express.js schematic automatically sets up a [Webpack dev proxy](https://webpack.js.org/configuration/dev-server/#devserverproxy) to make it easy to call the backend API.

Connect to an Express.js API from a React app in an Nx Workspace

When we talk about monorepos, we don't talk about the frontend specifically. Quite contrary: an Nx workspace can also host our backend apps. This opens up completely new possibilities in terms of exchanging code between the frontend and corresponding backend API. But before diving deeper into this topic, let's first learn about how we can use the `@nrwl/express` package to generate a [Express](https://expressjs.com/) based API application.

Create an Express Backend API in an Nx Workspace

Tuples are immutable so there is no way to add or replace items in tuples. There is a way to get around this by adding two tuples into one. 

Understand Immutability with Python Tuples

In this lesson, we will use Auth0 to generate a JWT that we can use to validate future requests to our server.

We will then return that token and test that it works when authenicated by our middleware.

During the lesson, we'll also briefly look at a strategy to keep your credentials out of source control using a .gitignore file. 

Get a JWT From Auth0 in Express to Be Used in Authentication

Sending a JSON Web Token is one way to valid your identity as a user of an API or service. In this lesson, we will see how to add an Express middleware which will check for a valid JWT and return a 401 Unauthorized error if not.

Add Middleware to Validate a JSON Web Token (JWT)

One way to secure API routes is by using JSON Web Tokens (JWTs) which are passed with each request and checked before a lesson is returned. To do this, you need an OAuth server to provide the signing and authentication of these tokens. Auth0 provides this for free for up to 7,000 users. 

In this lesson, we'll configure Auth0 and gather the details we need to be able to secure our API routes.

Configure an Auth0 API Authentication to Use with Your Server

Gatsby is a blazing fast static site generator built with React. Gatsby gives you all of the modern JavaScript tools you want; set up and ready to go out of the box.

gatsby

This lesson walks through how to update and query frontmatter data for Gatsby blog posts in order to display featured articles separately from recent articles.

Display Featured Articles through Frontmatter Properties on a Gatsby Blog

In this lesson, we'll look at how to handle errors in syncronous and asyncronous request handler functions. 

We'll also look at custom error middleware that allows for better control over how we return errors to our client based on whether we are in a production or development environment.

Handle Syncronous and Asyncronous Errors in Express

It's possible to pass configuration parameters to your Gatsby plugin. One use case is just allow the plugin to be used multiple times creating different queries that will be available for your site.

To do this you need to refactor the origin plugin code to accept this parameters and update the `gatsby-config.js` file to set them there.

Use configuration parameters for a Gatsby source plugin

Es posible pasar parámetros que ayuden a configurar tu plugin de Gatsby. Uno de sus caso de uso es permitir que el plugin se utilice multiples veces creando diferentes consultas que estarán disponibles para tu sitio.
Para esto es necesario refactorizar el plugin original para aceptar estos parámetros que son configurados mediante el archivo `gatsby-config.js`

Utilizar parámetros de configuración en un plugin para Gatsby

The plugin that you just implemented, each created node contains an attribute call `artwork_url` that references an URL for an external image. Is possible to directly use that URL to load the images in your site, but the images can big big and take too much time to load. You can optimize this images directly in your plugin to allow the site that use it to drop it directly into `gatsby-image`.


To accomplish the goal of optimizing the external images, your plugin will have to create a new type of node. This new file node will allow the user of your plugin to harness the power of the plugins `gatsby-plugin-sharp` and `gatsby-transformer-sharp` to perform transformations over the image field.


Optimize Remote Images in a Gatsby Source Plugin



Discover how to harness the power of Cursor IDE's Composer Agent feature to optimize your code. In this lesson, you'll witness an AI agent doing all the work to generate test suites, implement performance benchmarks, and create optimized function variations - all without writing a single line of code. You'll learn how to validate performance improvements through data-driven benchmarking, ensuring that optimizations are backed by concrete metrics rather than speculation. This hands-on demonstration showcases a groundbreaking approach to automated function development that combines the precision of test-driven development with the efficiency of AI-powered optimization.


Agent-Driven Development in Cursor: Testing, Benchmarking, and Optimizing Functions

This course is aimed for using `zod` effectively in projects based on TypeScript (both browser and node.js). The benefits you gain with this course is not just simply coding, but also understanding when/why/how should you perform runtime validation.

`zod` is the missing piece to TypeScript's capabilities, which can guarantee type-safety only in compile-time.

`zod` can be used whenever the compiler cannot guarantee what happens in runtime. And... it's a very frequent usecase, such as HTTP calls, websockets, etc.

In this course you get quickly up and running by:
1. using `zod` with primitives and objects
2. adapting `zod` quickly to existing projects thanks to automatic generators
3. changing the strategy frm type-first to schema-first
4. using error-throwing `parse` or non-error-throwing `safeParse` basing on your needs
5. applying `zod` to the most common usecase - validating API responses
6. handling errors the most convenient way (out of many!)

Take advantage of runtime validation with `zod`. Take advantage of the detailed lessons in this course 🔥

Effective Runtime Type Checks with Zod


Cursor can now automatically run commands in the terminal and walk step-by-step towards building out your entire project. You give it a goal, then it will suggest the commands you need to run and the files that you need to create and you can work with it to achieve what you're building. This lesson does a quick walkthough of using a Cursor Agent to build a project from scratch and guide it along the way. Cursor Agents definitely feel like a sneak peek at the future of programming!

Cursor Agents Initial Impressions - Allow an AI to Build Your Entire Project

Mock Service Worker is an API mocking library that allows you to write client-agnostic mocks and reuse them across any frameworks, tools, and environments.



Mocking WebSocket APIs with Mock Service Worker


While using anonymous functions might seem convenient, they can create difficulties when trying to identify performance bottlenecks during profiling. This lesson will demonstrate how named functions make it easier to pinpoint and address performance issues, ultimately leading to more efficient and debuggable code. Learning this practice will greatly improve your ability to locate and fix performance issues in complex projects.

Always Name Functions in JavaScript


When attempting to load the same module twice in JavaScript you'll hit a cache and code won't re-run. In scenarios where you actually do want to have state in your modules, you'll have to use a cache-busting technique by passing a query parameter to a dynamic import. This lesson walks through how to add a query parameter, how to add the appropriate types for loading dynamic modules in TypeScript, and when these techniques are valuable.

Import the Same JavaScript Module Multiple Times with Cache Busting



The include keyword in GitHub Actions empowers you to add custom variables to your matrix strategy, providing flexibility beyond standard configurations. In this video, we'll explore how include allows you to define specific combinations of variables, enhancing control over your workflow runs. You'll see how this feature enables you to tailor jobs for unique environments or scenarios not covered by the default matrix options. By leveraging include, you can efficiently manage complex build processes with greater precision. This technique helps you streamline your CI/CD pipeline, making it more adaptable to your project's evolving needs.

Use GitHub Actions Matrix Include for Complex Job Configurations

While running `zod` schema validation agains domain-rich objects, the error message saying that _a string is not a number_ might not be really useful.

Especially, when you need to provide a meaningful feeback to the user, e.g. after they have submitted a form with lots of data.

`zod` allows to customize messages on a very granular level. We can also extract repeatable customization to `zod` error maps.

Finally, in order to process an error message further (e.g. display it to the user), we need to handle the `zod` validation errors effectively. Especially, when a big object validation has failed and we could receive a handful of errors.

That's what we learn in this lesson. 🔥

Customize zod Error Messages and Handle zod Errors Effectively

customize zod validation messages, customize zod schema property messages, reuse error maps across different schemas, navigate through zod error objects

You might want to run `zod` schema checks in different styles.

Sometimes you prefer to conditionally throw the error - that's what `parse` does. But another time you'd prefer to receive a `boolean` property that determines whether the validation was successful or not - and perform further actions accordingly.

Additionally, the error-throwing API of `parse` works extremely well with [TypeScript assertion functions](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions). Their combination is just... perfect! 👌

That's what we learn in this lesson.

Use parse and safeParse Runtime Type-checks with zod

use zod parse function to conditionally throw ZodError, use zod safeParse to get a boolean value and run typescript type guard over success property

In this lesson we learn that TypeScript cannot guarantee correct shapes of responses. That's due to TS performing checks in compile-time, while the response will be availbale in runtime - when TS doesn't exist anymore.

In some situations, such as HTTP requests, runtime type checks such as `zod` are essential for providing quick feedback around data-related errors.

Understand where are the possible mistakes to make while using TypeScript with HTTP calls. Use `fetch` and `axios` along with `zod` schema checks.

Also, note that similar mistakes or mistakes could happen while using web storage (e.g. `localStorage`)

Validate HTTP API Response with zod, fetch and axios

use zod as an HTTP response validation tool along with fetch and axios in order to make sure that the response has expected data structure

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