Frontend Developer 路 Intern to senior
Frontend interviews combine language fundamentals (closures, the event loop, async code) with framework knowledge and an understanding of how the browser renders and updates the page.
93 questions
Utility types are built-in helpers that transform an existing type: Partial makes every field optional, Required the opposite, Pick keeps a set of keys, Omit removes them, and Record builds a key/value map.
Both integrate changes from one branch into another: merge keeps both histories and joins them with a merge commit, while rebase rewrites your commits so they appear on top of the target branch, giving a linear history.
Open the conflicted files, decide what the final code should be between the conflict markers, remove the markers, run the tests, then stage the files and continue the merge or rebase.
Mocking replaces a real dependency with a controllable fake so a test can run in isolation and check how the code interacts with it; use it for slow, non-deterministic or external dependencies, not for everything.
Recursively walk the array: when an element is an array, flatten it and append the result; otherwise append the element. An iterative version uses an explicit stack to avoid recursion limits.
Choose a real project with a technical or organisational challenge, explain your specific role and decisions with the STAR method, and finish with the result and what you learned.
Walk through how you noticed the issue, limited the impact, found the root cause, fixed it, and what you changed afterwards so the same class of bug could not happen again.
Choose a real mistake, take ownership, explain the impact, what you did to recover, and what you changed so it would not happen again.
Describe feedback that was uncomfortable but useful, explain how you responded, and show the measurable or observable improvement that followed.
Choose a genuine failure, explain why it failed, what you owned, how you recovered, and what you changed in future projects.
Show how you prioritized the essential outcome, communicated trade-offs, reduced risk and delivered without pretending everything could be done.
Show that you can defend a technical decision with evidence while remaining open to a better argument.
Keep the answer professional and future-focused: explain what you are looking for next without attacking your current or former employer.
The event loop is the mechanism that lets single-threaded JavaScript handle asynchronous work: it runs the call stack to empty, then runs all queued microtasks (promises), then takes the next task (timers, events) from the queue.
In JavaScript every object has an internal link to another object called its prototype, and property lookups walk up this prototype chain until the property is found or the chain ends.
Debounce waits until the user stops triggering an event for a set time before running the function; throttle runs the function at most once per time interval no matter how often the event fires.
useMemo caches the result of a calculation, while useCallback caches a function definition; both only recompute when their dependencies change.
Updating state triggers a re-render, while changing a ref's .current value does not; use state for data shown on screen and refs for DOM access or values that must persist without causing renders.
CSR renders in the browser after JavaScript loads, SSR renders the HTML on the server for each request, and SSG renders the HTML once at build time; SSR and SSG give crawlers and users content faster, which helps SEO.
Both download the script without blocking HTML parsing. defer waits until parsing finishes and runs scripts in document order; async runs a script as soon as it is downloaded, which can be before or after parsing and in any order.