 Courses from Yonatan Kra

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

The part pseudo class allows consumers of a web component to manipulate certain key elements inside the Shadow DOM.  In this lesson we will explore two use cases to using the part pseudo class.

Enabling CSS manipulation inside the shadow DOM using the part pseudo class

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

express

The main purpose of a web server is to export an api. The most common protocol is http requsts. In this lesson, we will learn how to benchmark your app's http api's using autocannon in order to be able to track down performance bottlenecks or inefficient code.

Benchmark http requests using autocannonjs

Big or non decimal numbers are sometimes hard to read inside code. Numeric separators are now part of the javascript specification and allow us to make numbers in our code more readable for humans.
In this lesson we will learn how to use numeric separators and the limitations of usage.

Javascript numeric separators

Angular is a development platform for creating applications using modern web standards. Angular includes a wealth of essential features such as mobile gestures, animations, filtering, routing, data binding, security, internationalization, and beautiful UI components. It's extremely modular, lightweight, and easy to learn.

angular

Sometimes you'd might need to render a component outside an angular application. One way to do it is by rendering a dynamic component outside the angular app. In this lesson we will learn how to do that and how to make sure data bindings work.

Rendering an angular dynamic component outside an angular app

In this lesson we will learn about how to define real private properties in javascript classes.

Private class properties in Javascript

Class properties can help you simplify your classes code. In this lesson we will see how to use class properties in javascript classes.

Assigning class properties in Javascript

The used heap size can be a valuable piece of information when it comes to improving your app's memory usage. In this lesson you will learn how to measure the used heap size in a nodejs application.

Measuring used JS heap size in nodejs

In this lesson we will see how to measure the used JS heap size in chrome. This can be used for various needs from performance debugging to production monitoring of apps.

Measuring used JS heap size in chrome

Sometimes you'd like to measure how two implementations compare in regards to run time.  In this lesson you will learn how to quickly do this using Console.time and constole.timeEnd.

Benchmark functions runtime in chrome console

Nodejs

In this lesson we will learn how to see your node server's code in chrome dev tools and also to add debug points to debug your nodejs app easily.

Debug a NodeJS App in Chrome Dev Tools

In this lesson you will learn how to use custom events to expose internal events from withing a web component.

Using Custom Events as a web component API

In this lesson, you will learn how to create an explicit API using methods on the web component itself.

Web components explicit API's using class methods

This is a list of web components lessons showing the technologies behind it and some practical ways to use it now in production.

Web Components

Frontend runtime optimization is heavily impacted by rendering.  Understanding the way the JS engine and the browser work is crucial for optimizing applications and understading how to avoid performance pitfalls.
This collection explains about the Critical Rendering Path, performance bottlenecks and practical solutions.

Critical Rendering Path

HTML 5 is the structure of our web pages. It is the markup that represents the DOM (document object model).

html

The Shadow DOM protects your components from style conflicts. The same protection also makes it hard for users to modify the inner style for their own needs. In this lesson we go over 3 ways to define API for a controlled manipulation of encapsulated styles.

Allow External Styling of a Web Component's Shadow DOM

Shadow DOM is part of the web components specification. It allows us to ship self contained components along with their style and isolate the component from global style while "protecting" the host application from styles defined inside the component.
In this lesson you will learn how to setup a shadow DOM and see the CSS encapsulation in action.

Avoiding CSS Conflicts via Shadow DOM CSS encapsulation

HTMLTemplates are part of the web components specification.  In this lesson we will learn what are HTML templates, how to use them and how to use the powerful HTMLTemplates slots inside a web component.

Build Flexible HTML with HTMLTemplates using Slots and Web Components

Custom elements are fun technology. In this video, you will learn how to set one up and running in less than 2 minutes.

You'll learn how to create a Custom Web Element (that extends `HTMLElement`) that renders text to the browser and respond to a click event listener.

Render Hello World Text with Custom Elements

Stop waiting for a single AI agent! This lesson demonstrates a powerful workflow to massively parallelize your AI-driven development in Cursor. Learn how to use tools like `file-forge` to package your project context, prompt advanced AI models (like Gemini in AI Studio) to brainstorm features and generate setup scripts, and then leverage a custom `git worktree` CLI tool (`wt`) to automatically launch an "army" of isolated Cursor instances, each tackling a different task on its own branch.

**Workflow Demonstrated / Key Benefits:**

*   **Bundle Project Context:** Use `file-forge` to create an AI-friendly representation of your codebase.
*   **AI-Powered Brainstorming & Scripting:** Prompt a reasoning model (e.g., Gemini via AI Studio) to suggest features *and* generate a shell script (`zsh`/`bash`) to automate setup.
*   **Automated Worktree Creation:** Execute the generated script which uses a custom `git worktree` CLI (`wt`) to:
    *   Create new branches and worktrees for each suggested feature.
    *   Install dependencies automatically (e.g., `pnpm install`).
    *   Launch multiple, isolated Cursor instances.
*   **Parallel AI Development:** Assign different features or implementation approaches to each Cursor agent (Composer) simultaneously.
*   **Efficient Monitoring:** Easily switch between active Cursor projects/worktrees using `Ctrl+R` or OS spaces.
*   **Seamless Integration:** Merge completed features back into your main branch using `wt merge` or use agents to commit, push, and create Pull Requests via the GitHub CLI (`gh pr create`).
*   **Boost Productivity:** Dramatically speed up iteration and experimentation by running multiple AI agents concurrently without conflicts.

This approach transforms your workflow, allowing you to explore multiple development paths simultaneously and integrate the best results efficiently using standard Git practices.

**Resources** 

https://www.npmjs.com/package/@johnlindquist/worktree
https://www.npmjs.com/package/@johnlindquist/file-forge

**Want to Learn More? Sign-up for my Cursor Workshop!**

https://egghead.io/workshop/cursor

John Lindquist

Swarm Intelligence: Massively Parallelize Your AI Agents in Cursor

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)

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

Yonatan Kra

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