Compiled Learning Objectives

WebSockets

• Stream live updates from a server using WebSockets.
• Discuss the trade-offs of using WebSockets or polling.
• Describe properties of message formats (e.g. including a command name).

Adding like/dislike

• Identify what data needs to be stored and exchanged between a client and server.
• Devise a scheme for differentiating messages with different meanings (e.g. a new message vs a new like).
• Contrast giving updated values as absolute values or relative changes.
• Implement an end-to-end feature involving data updates and reconciliation across a client and server.

Identifying common functionality

• Identify and explain the risks and costs of duplicate code.
• Identify which code is equivalent, equivalent with parameters, or unique.

Extracting common functionality

• Extract functionality used by multiple route handlers into a common function.

Continuation styles

• Compare different approaches to choosing how to handle potential request errors.

Extracting a middleware

• Identify and explain the risks and costs of manually calling code (e.g. authentication validators/extractors) from multiple route handlers.
• Explain the middleware pattern.
• Implement and wire up a middleware with Express.

Using existing middleware

• Use an existing middleware with Express.