Learn Cycle, Most and Puppeteer

OpenGraph images are the images you see when you paste a link into a social platform and it "unfurls" into an image, title, and description. This happens on Twitter, Discord, Slack, and many other platforms. This collection goes over everything from designing OpenGraph images in Figma, to implementing them in CodeSandbox, to returning headless browser screenshots from Netlify Functions, and finally using Cloudinary as a write-through cache. 

You will come away from this collection with the ability to ship an API that you can use on any of your sites, and also on-demand, that can generate images for not only OpenGraph unfurls, but also for Instagram, GitHub, and more. Using headless browsers with playwright to generate our images means we get full access to all the responsive power of CSS and all the logical power of JS to handle layout, importing assets like pngs, choosing different fonts, and more.

The image below is generated via the project you'll build and deploy in this course

![An example opengraph image](https://relaxed-payne-d1bfbe.netlify.com/opengraph?title=Building%20an%20OpenGraph%20image%20generation%20API%20with%20Cloudinary%20Netlify%20Functions%20and%20React&tags=figma,netlify%20functions,playwright&author=chrisbiscardi)

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

Building an OpenGraph image generation API with Cloudinary, Netlify Functions, and React

Puppeteer is a Node library which provides a high-level API to control headless Chrome or Chromium over the DevTools Protocol. It can also be configured to use full (non-headless) Chrome or Chromium.

puppeteer

When taking screenshots, it's important that the browser is big enough to show all of the content in the DOM that we want to screenshot. We can do this by setting the viewport.

Setting the viewport on a Playwright headless browser

In this lesson we are going to use the firstPaintTime metric from chrome's load times, as well as the navigation start from the W3C window metrics, to calculate how long it takes a page to paint. We will set up a quick function and test it out on google.com

Calculate a Page's First Paint Time with Puppeteer

It can be helpful when automating tests, metrics, and integration tools to know not only how much JavaScript there is on a page but to calculate how much is not being used. We are able to calculate the percentage of JS used by getting metrics from the window object. 

Get the Percentage of Unused JS on a page with Puppeteer

In this lesson we are going to use Google's Puppeteer to gather metrics about a page's load time. We'll use a high level date subtraction method as well as gather data from the window performance timing. Then see how throttling the network to 3G affects the page's load time. 

Get a Page's Load Time with Puppeteer

In this lesson we are going to send commands to the chromium browser with Puppeteer. These commands will enable us to calculate both the total number of CSS stylesheets used on the page and the ruleUsage for each of those stylesheets. With these metrics we will be able to calculate the percentage of unused CSS on the page. 

Get the Percentage of Unused CSS on a Page with Google's Puppeteer

Most.js is a toolkit for reactive programming. It helps you compose asynchronous operations on streams of values and events, e.g. WebSocket messages, DOM events, etc, and on time-varying values, e.g. the "current value" of an <input>, without many of the hazards of side effects and mutable shared state.

most

Unlike RxJS, Most does not include an observable-based AJAX helper utility. However, it can be very convenient to have one, because it allows you to use streams to do things like declaratively handling errors & setting up cancellation. In this lesson, we use currying & functional composition to create an Observable-based wrapper around the fetch API with Ramda & Most.

Create an Observable-Based Fetch Wrapper Using Ramda & Most

One of the more powerful functions for creating streams in MostJS is the `from` function.

In this lesson, we use `from` to create streams from various Javascript Iterables, take a look at how to throw generator functions into the mix and, for good measure, take a sneak peek at how we can limit our streams using a function called `take`.

As a bonus, we see what it looks like to use `Function.prototype.bind` for a quick and dirty way to partially apply arguments to a function.

Create Streams From Iterables With Most.js

Most provides many means for creating streams, the simplest of which is the `of` function. In this lesson, we demonstrate the use of `of` to lift a single value into a stream. We also show off the `just` alias of `of`, as well as, a common method for currying a function.


Create Streams From Single Values With Most.js

Cycle.js is a framework where your app is described as a simple function taking an event stream as input and outputting an event stream.

cycle

This lesson shows what can be learned next as a continuation of this course, and gives a recap on the core concepts: main for pure logic, drivers for side effects, run() to connect main and drivers, sources for read effects, sinks for write effects, and nesting Cycle.js apps to work as components.

Overview of Cycle.js

Cycle.js is a framework where your app is described as a simple function taking an event stream as input and outputting an event stream. 

Cycle.js builds on functional and reactive streams and is a JavaScript framework. What does that mean? In the course, André Staltz, the creator of Cycle.js, will explain it to us.

We'll start this course with an empty project and build out our own toy version of Cycle.js to understand exactly what's going on under the hood. When we have a solid base of how Cycle.js works we will move on to use the Cycle.js API and build an app using the Model-View-Intent pattern.

Cycle.js Fundamentals

Our app is not yet a BMI calculator, because it only has two sliders, but doesn't show the calculated BMI number. In this lesson we will learn how to export any stream from a child component and use it in the parent component, in order to display the BMI calculation on the DOM.

Export Values from Components through Sinks in Cycle.js

We added classNames to pre-processing and post-processing steps when calling the LabeledSlider, in order to instances independent of each other. It would be better if we could hide these steps away. This lesson introduces the isolate() helper function to achieve that.

Isolate Component Instances in Cycle.js

Once we have a labeled slider component inside the main function, we should be able to create another labeled slider. This lesson teaches how to accomplish that, and make sure those two instances work independently of each other.

Use Multiple Independent Instances of a Cycle.js Component

We have made a Cycle.js app for generic labeled slider which can be configured through props, but how can we reuse it in other Cycle.js apps? This lesson shows how we can embed any Cycle program inside a larger Cycle program in a very simple manner.

Use a Cycle.js Component in the main() Function

We are starting to get a better architecture for these UI apps. But we still have a problem of repeating code for the sliders, since they share so much in common in looks and functionality. This lessons shows how we can create a generic labeled slider as a main() function receiving properties as sources.

Create a Generic Cycle.js Component

We built the BMI calculator all inside one function: main(). As apps scale, we don't want main() to grow. We need an organized pattern where each function focuses on doing one thing. This lesson shows how we can easily refactor the main() function into three parts: Intent, Model, and View.

Organize your Cycle.js Application into the Model-View-Intent Pattern

So far we have been writing very small apps in Cycle.js. Let's start growing the size of the apps we build. This time, we will see how to build a simple Body-Mass Index Calculator. We'll see how as our application grows there are three distinct sections: handling read effects, handling write effects, and handling internal state.



Manage Multiple Observable Streams in Cycle.js

Let's see next how to use the HTTP driver to generate requests and capture responses. We will build a small app to fetch a single piece of data from a REST server and display that on the DOM.

Fetch Data using the Cycle.js HTTP Driver

This lesson shows how we can create a more interactive app: a counter display with buttons to increment and decrement it. We'll see how we can use the *xstream* `fold()` operator to remember previous values and combine them to create the next values. This is actually how you keep state in *Cycle.js*. 


Modify and Track State in Cycle.js

Now you should have a good idea what Cycle.run does, and what the DOM Driver is. In this lesson, we will not build a toy version of Cycle.js anymore. Instead, we will learn how to use Cycle.js to solve problems. We will start by making a simple Hello world application.

Read Text Input in a Cycle.js Hello World Application

Creating powerful and context-aware tools for Cursor IDE becomes straightforward when leveraging information directly from your current project. In this lesson, you'll learn how to build a custom MCP (model context protocol) tool that intelligently requests essential details—such as the current project path and conversation summaries—from your Cursor project.

Workflow demonstrated in this lesson:

- Define MCP tool parameters to request specific project details.
- Pass project path and conversation summaries into your MCP tool.
- Automatically write or update files within your current project using these parameters.

Key benefits:

- Automate tasks with precision based on your active project's context.
- Simplify interactions by creating AI-driven CLI commands tailored to your needs.
- Open endless possibilities for integrating external APIs and advanced automation.

Through this practical demonstration, you'll gain a versatile technique for enhancing your development workflow in Cursor IDE.

[https://github.com/johnlindquist/mcp-cursor-tool-starter](https://github.com/johnlindquist/mcp-cursor-tool-starter)

John Lindquist

Build MCP Tools Using Project Context for Custom Cursor IDE Automation

Setting up custom MCP (Machine Command Protocol) servers in Cursor can involve tedious steps, such as configuring node paths or referencing additional commands. This lesson shows how to streamline this process by bundling your MCP server directly into a standalone executable.

Workflow demonstrated in this lesson:

- Use a simple MCP server project starter.
- Run a single bundling command to create an executable.
- Right-click the generated executable, copy its full path, and add that directly to your Cursor settings.

Key benefits:

- Eliminates the need for complex node path configurations.
- Simplifies the setup and integration of custom MCP servers into Cursor.
- Makes the server executable instantly accessible within your Cursor environment.

By following this streamlined approach, you can quickly and easily integrate custom MCP servers into Cursor, making your development workflow cleaner and more efficient.

[https://github.com/johnlindquist/mcp-cursor-tool-starter]()

Easy MCP Server Setup in Cursor IDE with Bundled Executables

TanStack Router is the foundation for TanStack Start, which is gaining significant attention due to its innovative approach to application development.

This course focuses on getting effective TanStack Router, a modern and scalable routing solution for React applications. You will learn how to:
- set up and scaffold new applications,
- use file-based routing
- create nested routes
- manage dynamic route parameters and more.

The course covers advanced features like route loaders, caching strategies, and lifecycle hooks, which are crucial for enhancing application performance and user experience.

By understanding TanStack Router, you can build more efficient, type-safe, and maintainable applications, leveraging its integration with data fetching libraries like TanStack Query.

This knowledge is essential for developers looking to improve their routing skills and stay ahead in the field.

Tomasz Ducin

Up and Running with Tanstack Router and React

Learn TanStack Router for React: set up apps, use file-based routing, manage routes, and boost app performance.


In this lesson, we explore how TanStack Router integrates with the [native browser history API](https://developer.mozilla.org/en-US/docs/Web/API/History) to manage navigation.

As we navigate through different routes, the URL changes are stored in the browser's history, allowing users to use the forward and backward buttons to traverse their navigation history.

This functionality also **enables permalinks**, meaning users can copy and paste URLs to access specific routes directly.

Additionally, we learn how to programmatically interact with the history object to move forward or backward through the navigation stack, enhancing the user experience by providing full control over navigation actions.

This compatibility with the native history API ensures that TanStack Router applications behave similarly to traditional websites, offering a seamless and intuitive user experience.

Browse History in Tanstack Router

Browse history in TanStack React Router using the native history API for seamless navigation

In this lesson, we explore how to hook into TanStack Router's lifecycle hooks to execute custom logic during route changes.

The hooks we'll look into are: `onEnter`, `onStay`, and `onLeave`, which are triggered when entering, staying within, or leaving a route, respectively.

All hooks receive a detailed match parameter, providing information about the route's path, ID, and tons of other details.

This allows for the implementation of features like animations or logging when navigating between routes.

We also learn how to use these hooks to track and manage state changes as users interact with the application, making it easier to implement complex behaviors based on route transitions.

Hook into Route Lifecycle Hooks in Tanstack Router

Hook into TanStack React Router's lifecycle hooks for custom route logic and animations.

In this lesson, we learn how to handle not found errors in TanStack Router by using the `notFoundComponent` at both nested and global levels.

To trigger the display of a `notFoundComponent`, we must throw a specific error using the `notFound` function within a loader or other lifecycle method of a route. This approach allows us to provide custom error messages for specific routes or globally across the application.

We explore how to define a notFoundComponent within a specific route's configuration and how to set a `defaultNotFoundComponent` at the router global level, which applies to all routes unless overridden locally. This flexibility ensures that users receive meaningful feedback when encountering non-existent routes.

Provide NotFoundComponent at Nested Route or Global Level in Tanstack Router

Handle notFound errors in TanStack Router with notFoundComponent at nested or global levels.



In this lesson, we learn how to access dynamic route parameters using the `useParams` hook in TanStack Router.

When used with a specific `Route` object, `useParams` provides type-safe access to route parameters, ensuring that TypeScript knows the exact types of these parameters.

This approach eliminates the possibility of undefined/optional values, making it safer for accessing parameters like `employeeId`.

However, when using `useParams` globally without specifying a route, it requires an options object with `{ strict: false }`, which reduces type safety.

In this case, the hook can access parameters from any route in the application, but it does not guarantee their existence or type. This flexibility allows components to be reused across different routes, but it requires careful handling of potential errors.



Access Dynamic Route Parameters with useParams in Tanstack Router

Access dynamic route parameters with useParams in TanStack React Router for type-safe routing.

In this lesson, we learn how to reorganize file-based routes in TanStack Router to accommodate nested routing structures.

We explore how to create additional nested routes by converting files into directories, allowing for further nesting.

For example, to create a nested route like `/employees/$employeeId/edit`, we can create a **directory** (!) named `$employeeId` and place an `index.tsx` file inside it to define the route component for this nested route.

This approach provides flexibility in organizing files while maintaining the convention that file names and locations align with route paths. We also see how to adapt existing components and loaders to work with these reorganized routes, enabling features like edit forms or delete actions (or whatever) within nested routes.


Reorganize File-Based Routes in Tanstack Router

Reorganize file-based routes in TanStack Router for flexible nested routing.



In this lesson, we learn how to parametrize the loader for a nested route in TanStack Router.

We focus on a nested route like `/employees/$employeeId`, where the `$employeeId` is a **dynamic parameter**.

To fetch data for this route, we use a `loader` function that accesses the `$employeeId` parameter. This is achieved by using the params object available in the `loader` function, which contains the dynamic segments of the URL. We then use this parameter to call a function like `getEmployeeById`, which fetches specific employee details from an API.

We highlights that TanStack Router **automatically infers types** for these parameters, ensuring type safety for nested routes.

Parametrize Route Loader for Nested Route in Tanstack Router

Parametrize nested route loaders in TanStack Router using path parameters

In this lesson, we learn how to create nested routes and outlets in TanStack Router using file-based routing.

We start by creating a new `employees` directory and files to represent nested routes, such as `/employees/$employeeId`. The `$` symbol is used to denote dynamic parameters.

We then use the `<Link>` component from TanStack Router to create links to these nested routes, passing necessary parameters.

To render the nested content, we use the `<Outlet>` component (nested), which automatically renders child routes. This approach allows us to dynamically display stuff under a nested route.

All the time, the TanStack Router generator automatically updates the route tree based on file changes - our routing configuration remains consistent 🔥



Create Nested Route and Nested Outlets in Tanstack Router

Create nested routes and outlets in TanStack Router using file-based routing

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