5 HARD Frontend Interview Questions In 5 Minutes

Summary

This video delves into five senior frontend interview questions, offering insights and mental models to help candidates excel. It covers essential topics such as code splitting, dynamic imports, and the rehydration process for server-rendered HTML. The explanation of the event loop clarifies how asynchronous tasks are managed, while CSS-in-JS addresses potential styling conflicts in component frameworks. Additionally, it explains the nuances of script tag attributes like defer and async, tying these concepts to the critical rendering path. This comprehensive approach equips viewers with the knowledge to tackle technical interviews confidently.

Takeaways

• 😀 Code splitting breaks an application bundle into smaller chunks that can be lazy loaded, improving performance.
• 😀 Understanding the dependency graph is crucial for effective code splitting, allowing independent packaging of modules.
• 😀 Dynamic imports allow loading modules as functions, enabling on-demand fetching and execution.
• 😀 Rehydration makes server-rendered HTML interactive by attaching event listeners and synchronizing with the client component structure.
• 😀 The client-server interaction involves initial HTML loading followed by the fetching of JavaScript bundles for full interactivity.
• 😀 The event loop manages the execution order of code, ensuring that synchronous code runs first, followed by microtasks and then tasks in the queue.
• 😀 CSS-in-JS resolves conflicts in styles by generating unique class names, ensuring no CSS conflicts between components.
• 😀 The 'defer' attribute in script tags delays script execution until after the first render, improving loading performance.
• 😀 Understanding critical rendering paths helps optimize the loading of HTML, CSS, and JavaScript, facilitating faster rendering.
• 😀 For more technical interview preparation, additional resources and video links are available for further exploration.

Q & A

What is code splitting and why is it important?

Code splitting involves breaking down an application bundle into smaller, independent chunks that can be loaded on demand. This technique improves performance by reducing initial load times, allowing users to access parts of the application without waiting for the entire bundle.

How does the dependency graph relate to code splitting?

The dependency graph is a tree-like structure created based on module imports. It helps identify which sections of the code can be packaged independently, facilitating the code splitting process.

What is the rehydration process in web development?

Rehydration is the process of making server-rendered HTML interactive. It involves attaching event listeners to the pre-rendered content and rendering the corresponding component structure on the client side.

Why is rehydration necessary when using server-side rendering?

Rehydration is necessary because server-side rendering provides fully rendered HTML but lacks interactivity. By rehydrating, the client-side application can attach the necessary functionality and event handling to the already displayed content.

What role does the event loop play in JavaScript execution?

The event loop manages the execution of asynchronous code in JavaScript. It processes synchronous code first, then moves to the microtask queue for promise resolutions, and finally handles tasks from the task queue like `setTimeout`.

How can understanding the event loop help during technical interviews?

Understanding the event loop helps candidates predict the order of execution for various types of code, allowing them to accurately answer questions about asynchronous behavior and timing in JavaScript.

What problem does CSS-in-JS solve?

CSS-in-JS solves the problem of CSS conflicts in component-based frameworks. By allowing styles to be defined within JavaScript, it generates unique class names, ensuring that styles do not interfere with one another.

What does the `defer` attribute do in a script tag?

The `defer` attribute allows the script to be downloaded in parallel with other resources but defers its execution until after the first render of the page is complete, improving load performance.

How do `async` and `module` script tags differ from regular scripts?

The `async` attribute allows scripts to be executed as soon as they are downloaded, potentially out of order, while the `module` attribute is a type of deferred script that is executed after the first contentful paint but maintains the benefits of modern JavaScript modules.

What can developers do to prepare for technical interviews based on this content?

Developers should familiarize themselves with these concepts, practice explaining them using mental models, and review additional technical questions available through the provided resources.