Learn Chai, Hapi and Requirejs

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

In this lesson, Mark will summarize why it is good to use RequireJS for managing JavaScript dependencies. We'll go over an example of a plain vanilla JavaScript implementation of jQuery, and refactor the code to use RequireJS.

WTF is RequireJS?

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.

chai

In this lesson, you will learn how to verify your API server is returning HTTP 400 responses when clients submit incorrect data. Returning HTTP 400 ensures that your clients are notified of the incorrect usage. Testing for them ensures your API returns errors instead of incorrect responses when supplied with incorrect data.

Test for HTTP 400 responses with Mocha and Chai

In this lesson, we will use Chai's request method to test our Node application's API responses.
By the end of this lesson, you will know how to:
- install the prerequisites to use mocha and chai in your application
- test for HTTP status response codes
- test for a string of text on a page
- test for a json response and validate the properties of the object
- write tests that not only verify the response of your application, but the behavior as well


Test Node RESTful API with Mocha and Chai

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

mocha

Writing great ES6 style Promises for Node.js is only half the battle. Your great modules must include tests as well to ensure future iterations don't break them. In this lesson, I show you a simple ES6 Promise in Node.js, then walk you through creating tests in Mocha using chai and chai-as-promised to test both resolve and reject methods.

Testing ES6 Promises in Node.js using Mocha and Chai

A rich framework for building applications and services hapi enables developers to focus on writing reusable application logic instead of spending time building infrastructure.

hapi

hapi makes handling POST and PUT payloads easy by buffering and parsing them automatically without requiring additional modules or middleware. This video will demonstrate how to handle JSON and form based request payloads via hapi's route configuration.

hapi.js - POST and PUT request payloads

hapi automatically responds with JSON for any error passed to a route's `reply()` method. But what if your application needs errors rendered in HTML? This lesson shows how to implement friendly HTML error messages using hapi extension events.

hapi.js - Friendly error pages with extension events

hapi supports request validation out of the box using the joi module. Request path parameters, payloads, and querystring parameters can be validated with joi's simple, yet powerful, notation. This lesson covers the basics of validating requests using joi.

hapi.js - Request Validation with Joi

hapi has built-in support for parsing cookies from a request headers, and writing cookies to a response, making state management easy and straight-forward. It even has built in support for cookie encryption and auto detects when a cookie contains JSON, parsing or stringifying automatically.

hapi.js - Managing State with Cookies

Instead of using middlware, hapi provides a number of points during the lifecycle of a request that you can hook-in to provide additional functionality, called "extension events". This lesson will give you an introduction to using extension events, and show how they can be used to manipulate the request or response in-flight.

hapi.js - Extending the request with lifecycle events

hapi is a battle-tested, full-featured, framework for building web applications and services with Node.js. With integrated support for essentials like authentication, caching and validation, and a powerful plugin system, hapi is ideal for projects and teams of any size.

This course will introduce hapi, some of it’s plugins, and guide you through many of hapi’s core features.

Introduction to Node Servers with Hapi.js

View engines, or template engines, allow you to maintain a clean separation between your presentation layer and the rest of your application. This video will demonstrate how to use the vision plugin with hapi to enable template support.

hapi.js - View engines 

hapi does not support serving static files out of the box. Instead it relies on a module called Inert. This lesson will cover serving static files using Inert's custom handlers.

hapi.js - Serving static files

hapi's reply interface is one of it's most powerful features. It's smart enough to detect and serialize objects, buffers, promises and even streams. This video will demonstrate first hand how to use the reply method to send your data to the client, no matter the format.

hapi.js - Replying to Requests

Think of hapi's `reply()` function as "what you want to say" and the `response` object as "how you want to say it". While `reply` controls the payload sent to the client, the `response` object will allow you to control how the client interprets the payload by manipulating status code, content type, state and more.

hapi.js - Using the response object

Routing is a fundamental aspect of any framework. In this lesson, you'll learn how to use path parameters in hapi's router. We'll also touch on how the router uses specificity to order routes internally.

hapi.js - Route parameters

hapi doesn't ship with logging support baked in. Luckily, hapi's rich plugin ecosystem includes everything needed to configure logging for your application. This video will introduce good, a process monitor for hapi, and good-console, a reporter for good that outputs to standard out.

hapi.js - Logging with good and good-console

hapi is a rock solid server framework for Node.js. Its focus on modularity and configuration-over-convention makes it the perfect match for any size development team. This video will introduce you to hapi by showing you the bare minimum needed to run a hapi server.

hapi.js - Up and running

Now that you've got everything set up with mocha and chai, it's time to actually write tests. In this lesson you'll learn how to use `describe` and `it` to outline your tests and make sure you don't break your library in the future.

Unit Testing with Mocha and Chai

Every dependable library needs to have tests to ensure that you don't push accidental bugs. In this lesson, see how you can set up mocha and chai to start testing your library.

Setting up Unit Testing with Mocha and Chai

RequireJS is a JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, like Rhino and Node. Using a modular script loader like RequireJS will improve the speed and quality of your code.

requirejs

RequireJS provides a clean way to load and manage dependencies for your Javascript applications. This video examines the first steps towards using RequireJS.

Introduction to RequireJS

AI is amazing for generating code, but often leaves us staring at functions and libraries we've never seen before. This creates a huge problem: When things break (and they will break), we're lost. We don't understand the individual pieces, let alone how they interact. Knowing one part isn't enough; we need to see how unfamiliar components work together.

The solution? Real-world examples.

This lesson introduces ghx, a tool I built to do exactly that. ghx searches GitHub, finding actual code examples that use the specific combinations of functions and libraries that are tripping you up. Instead of generic documentation, you get concrete implementations. You can find the ghx repository at https://github.com/johnlindquist/ghx.

Here's the workflow we cover:

Identify the Unknown: Pinpoint the AI-generated code you don't understand – specific functions, libraries, or their interactions.

Search with ghx: Use ghx to search GitHub for examples using those terms together. ghx finds repos where those elements co-exist.

Consolidate Examples: ghx combines the relevant code snippets from those examples into a single, digestible file.

Ask the AI (Again, but Better!): Feed this consolidated code to an AI (like a coding-focused model in an AI studio). Now, instead of asking general questions, you can ask targeted questions based on real-world usage:

"Explain how these functions are used together in these examples."

"What are some common use cases for this combination of libraries?"

"Show me alternative code snippets that achieve the same result."

"Can you identify potential problems or areas for improvement, based on these examples?"

Iterate. Use your improved understanding to make changes, and then repeat the process to debug.

By leveraging ghx and targeted AI prompting, we transform from being lost in a sea of unfamiliar code to actively learning from how others have solved similar problems. We gain a deeper understanding of our AI-generated codebase, making debugging, modification, and future development far more manageable. This gives you the tools to understand, debug and improve your own code.

John Lindquist

How to Work with AI-Generated Code You Don't Understand

In this less we create a custom Zod schema using `z.custom`.

The example case covers room numbers validation: it must start with an uppercase letter followed by three digits. `z.custom` allows the creation of a brand new custom schema with a callback function that returns a boolean indicating validity.

We highlight a challenge with type inference in Zod's custom schemas: callback parameter types don't get aligned automatically - type-safety must be explicitly defined using type parameters.

We run tests against various room numbers and demonstrate how to effectively validate inputs and manage error messages.


Tomasz Ducin

Create Custom Zod Schemas and Validate project-specific data

Create custom validation logic in Zod using z.custom, for primitive values, ensuring type safety and proper error messages for room numbers.


Excessive properties refer to any additional attributes that are not explicitly listed in an object schema. When creating an object based on a schema, it is important to ensure that only the defined properties are included.

In TypeScript, if an object is created with an extra property that isn't defined in the schema, TypeScript will not raise an error unless the type is explicitly annotated. When the type is annotated, TypeScript will issue an error indicating that the extra property is not allowed.

Zod provides a strict utility to enforce similar checks. This feature ensures that only specified properties are allowed in an object schema. When unnecessary properties are added at both the top level and within nested schemas, Zod will throw errors indicating unrecognized keys.

Adding an unrecognized property to a Zod schema results in an error message that specifies which keys are not recognized. Applying strict checks on nested schemas ensures that all levels of the data structure are validated correctly.


Make Excessive Object Properties Fail on Zod Validation

Prevent excessive properties in TypeScript and Zod schemas using strict checks for better data validation

In this lesson we discuss how Zod works with TypeScript to handle special types like `undefined`, `null`, `any`, `unknown`, `never` and `void`.

We modify our room booking schema to demonstrate the use of `optional` and `nullable` Zod utilities.

By using `.optional`, we allow a property to be either its _original type_ or `undefined`. With `.nullable`, we allow it to be either its _original type_ or `null`. Finally, `.nullish` allows a value to be either its _original type_, `null`, or `undefined`.

For all cases, we run tests to show how these schemas work in practice, as well as how TypeScript infers types.


Declare Lack of Value in zod (optional, nullable and nullish)

use Zod for TypeScript schemas, including handling undefined, null, and special types like optional and nullable values, as well as any, unknown never and void

In this lesson we make use of partial validation of large and nested schemas in Zod.

Instead of creating many small schemas, which can complicate maintenance, Zod allows for the extraction of specific parts of a schema using the concept of ".shape". It "unwraps" the object schema, enabling access to sub-schemas within specific properties.

Additionally, we can use the `.unwrap` to get into element schemas of altered schemas such as `.optional` or `.array`.

Simplify working with complex schemas without the need to break them into hundreds of small schemas.

Use Zod Schemas partially using shape and unwrap

Manage large and nested Zod Schemas by extracting partial validations using shape and unwrap utilities

In this lesson we cover implementing sets and maps in Zod.

Using `z.set`, a schema for string-based amenities is created. We demonstrate how validation works by intentionally introducing errors and customizing error messages for better clarity.

Next, a map is created for existing guestDetails schema using `z.map`, with string keys and an existing `z.object`-based schema. The validation process is shown again by deliberately breaking the schema, such as omitting the age property, which triggers appropriate error messages.


Validate maps and sets using Zod schemas

Use sets and maps in Zod for schema validation, ensuring type safety for both keys and values.

In this lesson we'll use a few predefined schemas which will serve as constituents to create union and intersection schemas.

Three room booking schemas are defined: _single_, _double_, and _suite_. Each schema has slight differences in the structure.

The `z.union` utility is used to create a union of these schemas, allowing for validation against any of them. Type inference (using `z.infer`) for the room booking schema produces a union of object literals, exactly like in TypeScript.

We also create an intersection using `z.intersection`, combining room booking details with discount information.

These techniques enhance data validation and allow to make `zod` aligned even more with `TypeScript`.


Define Unions and Intersections with Zod

implement unions and intersections in Zod schemas for example domain related objects, enhancing TypeScript validation with clear examples

This lesson demonstrates how to provide runtime type-safety for arrays in TypeScript applications.

First we need to understand the challenges behind ensuring array type-safety in TypeScript. We explain how TypeScript infers arrays with an undefined length, making it difficult to guarantee that array accesses are safe.

Zod schemas provide the `z.array` to define arrays of various element types. 

We compare how utilities such as `.min`, `.max` and `.nonempty` get reflected in inferred TypeScript types, and how zod processes the validation.


Declare Precise Array Types within Zod Schemas

Provide array type safety in TypeScript using Zod schemas, including handling non-empty arrays for better validation

In this lesson we make string-based schemas more specific using Zod in TypeScript. We focus on defining allowed values for a room type, showing how to use literals and enums effectively.

Zod's `z.literal` method allows us to specify a single allowed value for a string schema. For example, if we want to define a room type as `"premium"` and make it backward-type-safe in TypeScript, we can use `z.literal("premium")` to ensure that only this value is valid.

`z.enum` lets us define a set of allowed string values. This is useful when we have multiple options for room types, like `"standard",` `"premium"` or `"childrenFriendly"`. 

`z.enum` creates a union of TypeScript-compatible string literals, making it easy to validate against multiple values. Zod enums can be used to extract or exclude specific values from the enum.

Finally, zod's `z.nativeEnum` a native enum creates an equivalent of TypeScript's native `enum` ("real enums", we could say).

We can validate against all these values just like we do with literals and enums.


Work with Zod Literals and Enums Effectively

Use Zod for string schemas in TypeScript, including literals, enums, and native enums for room type validation

In this lesson, we dive into the Zod's `refine` utility, allowing defining more complex schema validation **on top of existing schemas and utilities**.

Sometimes, we need special validation rules for our applications to work correctly. The `refine` utility lets developers create their own validation rules. This method's uses a callback to check if the input is valid. We also create meaningful messages when something doesn’t meet the validation rules.

We use a practical example involving a room booking schemawith `dueDate` and `price` property refinement.


Apply Schema Custom Refinement with Zod

Enhance your TypeScript validation skills with Zod's refine utility for custom room booking schemas, focusing on date and price validation.


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