Senior Frontend Web Developer Interview Questions and Answers

promise.all waits for all promises to resolve, while promise.race waits for the first promise to resolve or reject

• promise.all resolves when all promises in the iterable have resolved

• promise.race resolves or rejects as soon as one of the promises in the iterable resolves or rejects

• Example: Promise.all([promise1, promise2, promise3]) will wait for all three promises to resolve before resolving itself

• Example: Promise.race([promise1, promise2, promise3]) will resolve or reject as...read more

Improving frontend optimizations involves minimizing file sizes, reducing HTTP requests, utilizing caching, and optimizing images.

• Minimize file sizes by removing unnecessary code, using minification tools, and compressing assets.

• Reduce HTTP requests by combining files, using sprites, and lazy loading resources.

• Utilize caching techniques like browser caching, server-side caching, and CDN caching.

• Optimize images by choosing the right format, resizing images appropriately, and u...read more

There are several promise methods in JavaScript, including .then(), .catch(), .finally(), and more.

• Common promise methods include .then(), .catch(), and .finally()

• Other promise methods include .all(), .race(), and .resolve()

• Examples: promise.then(), promise.catch(), promise.finally()

JWT is a popular method for authentication and authorization in web development.

• JWT stands for JSON Web Token, a compact and self-contained way to securely transmit information between parties as a JSON object.

• JWTs consist of three parts: header, payload, and signature.

• Authentication is the process of verifying the identity of a user, while authorization determines what actions a user is allowed to perform.

• JWTs are commonly used in stateless authentication systems, where the ...read more

Use recursion to get unique keys in nested object

• Create a function that takes in an object as input

• Use recursion to iterate through the object and store unique keys in a Set

• Return an array of unique keys from the Set

Debouncing in Javascript is a technique used to limit the number of times a function is called, typically used for handling events like scroll or resize.

• Debouncing involves setting a delay before a function is executed after the last time it was called.

• It helps in optimizing performance by preventing unnecessary function calls, especially for events that trigger frequently.

• Example: Implementing a debounce function for handling scroll events to improve performance.

Closures are functions that have access to variables from their outer scope even after the outer function has finished executing.

• Closures allow functions to access variables from their parent function's scope

• They maintain references to their outer scope even after the outer function has finished executing

• Closures are commonly used in event handlers and callbacks

Caching is a technique used to store copies of frequently accessed data in order to speed up retrieval times.

• Caching helps reduce the load on servers by serving cached content instead of generating it from scratch.

• Common types of caching include browser caching, server-side caching, and CDN caching.

• Examples of caching libraries/tools include Redis, Memcached, and Varnish.

• Cache invalidation is an important aspect of caching to ensure that stale data is not served to users.