100 Front End Interview Questions Challenge

Demonstrate pass by value vs pass by reference in JavaScript, illustrating primitive vs non-primitive data, how arrays and objects copy, and how to clone without mutation using spread or stringifying.

explain why global variables are discouraged in front-end development, noting dom globals such as window and document, node's global, and that globals are easily manipulated and create scope risks.

Explore JavaScript strict mode and use strict, which enforces best practices, prevents global variable creation, bans deleting properties and duplicate parameter names, and turns errors on mistakes to reduce bugs.

Explore anonymous functions in JavaScript by contrasting them with named functions, showing how to store a function in a variable, pass it as a reference, and invoke it later.

Explore callbacks and higher-order functions in JavaScript, showing how to pass a function to map and a promise, call them later, and manage synchronous and asynchronous flows.

Explore closure as a function that returns another function to hide a private counter, preventing global scope access while enabling controlled state updates through an inner function.

Explore how to empty an array in JavaScript using multiple techniques, including reassigning to an empty array, setting length to zero, and using splice, pop, or shift in loops.

Explain the difference between undefined, null, and undeclared with code examples. Show how accessing non-existent properties yields undefined, how undeclared means no definition, and how null represents no value.

Understand how JavaScript represents not a number (NaN), explore cases like zero divided by zero and string-to-number conversions, and learn the isNaN check to detect non-numeric values.

discover the five http status code groups (100, 200, 300, 400, 500), their meanings, and how to discuss and debug network calls in asynchronous front-end development.

Explore how setTimeout and setInterval create delayed and repeated actions in JavaScript, with hands-on examples showing how to start, stop, and manage timers using clearTimeout to control asynchronous code.

Master promises as a JavaScript tool for handling asynchronous data, including fetch API and user input, showing resolve and reject, chaining with then/catch, and improving readability with async/await and try/catch.

Learn how async/await simplifies promise handling by making asynchronous fetches appear synchronous, reducing nesting and enabling cleaner code with try/catch error handling.

Learn how responsive web design creates a single application that adapts to multiple devices by using media queries, CSS flexbox or grid, and native CSS layouts.

Explore the box model and how padding, border, and margin shape every element's space, positioning, and layout, with insights from the inspector and computed properties.

Learn to create a circle in CSS using a div with equal height and width, a background color, and border-radius 50%. Explore color formats like hex, rgb(a), and CSS variables.

Define the problem of a slow app and use browser tools like Lighthouse to diagnose performance issues, then optimize images, bundles, and network calls.

Explore the SOLID principles: single responsibility, open-closed, Liskov substitution, interface segregation, and dependency inversion with practical front end examples to write maintainable, extensible code.

Master debugging by using browser inspector tools, console logs and console table, writing unit tests, and leveraging devtools network, performance, and audits to proactively fix bugs.

Address the 'last thing you learned' red flag by highlighting progress in progressive web apps, service workers, and offline capabilities, while showing framework experience with view, Vuex, and material libraries.

Learn how agile and Scrum drive fast, iterative development with two-week sprints, standups, planning, demos, and stakeholder reviews, plus guidance on product owner roles and Scrum certifications.

Explore frontend tooling, from the terminal to customizable VS Code extensions and formatting on save. See how Postman, browser extensions, and mock data fill streamline API calls and collaboration.

Evaluate how to answer why you should hire me by highlighting what makes you unique, how you raise the team, and your track record of mentoring and passion.

Learn to discuss mistakes clearly in interviews, explain how you handled them, and demonstrate learning and corrective actions to deliver a quality product under pressure.

discover what code quality standards teams follow and learn the interview questions that reveal branching strategies, unit testing, end-to-end testing, feature toggles, CI/CD, and QA processes.

Deliver a final statement that explains why you are perfect for the role by highlighting core technologies from your side projects, continued learning, and your mentoring of junior devs.

Carry a leather binder with a notes section and resume copies, but avoid taking live notes to preserve eye contact and momentum; use recruiters for follow-up questions.