Exit Ticket: Day 6 - Express and Handling Asynchronous Code

day6-exit-ticket.md

Exit Ticket: Day 6 - Express and Handling Asynchronous Code

You should be able to:

• Describe the role of a client, a server, and HTTP
• Describe Express middleware, requests, and responses
• Handle URL params in an Express route
• Know when and why you would use app.use and next in your Express app
• Explain the purpose of using async/await & Promises

In your own words, what is a server?

• A HTTP server listens for HTTP requests and sends HTTP responses.

Reference: MDN: What is a web server?

What is the purpose of the package.json file in a Node project?

• Store a list of dependencies for the project
• Give the project a name
• Store metadata about the project
• All of the above ☑️
• None of the above

Reference:

• See the section "Properties of a package.json file" here.
• Node: What is the file package.json?

What is Express?

• Node web framework for handling requests ☑️
  • Provides mechanisms to:
    • Write handlers for requests with different HTTP verbs at different URL paths (routes)
    • Set common web application settings like the port to use for connecting
    • Add additional request processing “middleware” at any point within the request handling pipeline
• JavaScript runtime environment
• JavaScript library for building user interfaces
• An ORM

Reference:

• Express.js documentation
• MDN: Express/Node introduction
• tutorialspoint: ExpressJS Overview

Which of the following statements are true about Express Middleware?

• An example of it could be app.use ☑️
• It happens between the request and response ☑️
• Only one middleware function can be called per request-response cycle
• An example of it could be app.get ☑️
• It sometimes runs after the response is sent

Reference:

• Express: Using middleware
  • In reference to app.get, in this doc, it says, "Express is a routing and middleware web framework that has minimal functionality of its own: An Express application is essentially a series of middleware function calls." Technically, since Express is built on top of and leverages Node, Express sits in between the request and response.
• Express: Writing middleware for use in Express apps
• Express: app.use()
• A function that receives the request and response objects of an HTTP request/response cycle (i.e. (req, res, next) => {...}).

What is a Promise?

• A function that runs asynchronous code
• A keyword that marks a function as having asynchronous code
• A callback function that executes after an asynchronous operation finishes
• An object that represents the eventual completion of an asynchronous operation and its resulting value ☑️

Reference:

• MDN: Promise
• MDN: Using Promises

Which of the following statements is true about async/await?

• You can use await outside of an async function
• async functions are not Promises when the return value is not a Promise itself
• Inside of an async function, the code behaves synchronously ☑️
• async functions are synchronous

Reference:

• MDN: Making asynchronous programming easier with async and await
• MDN: async function