Frontend

TypeScript: what is the difference between the types `any`, `unknown`, and `never`?

Vue 2 and Vue 3: what architectural limitations of Vue 2's reactivity forced Evan You to rewrite the engine using `Proxy`?

JavaScript: what is the difference between `prototype` and `__proto__`?

Vue 3: what is the fundamental difference between `ref` and `reactive`, including their underlying workings?

If `Proxy` is so good, why does Vue 3 still have `ref`?

Analyze the provided Vue code: which variables are reactive, where reactivity is lost, and how to fix it?

When optimizing the loading of a heavy frontend application with 150 small icons, should icons be combined into a single sprite or use CSS-inlining when using HTTP/2 or HTTP/3?

Can `debounce` be combined with `AbortController`?

In the provided Vue code, will the template update when clicking the button?

If you create a `watch` or `computed` inside `setup`, what will happen to them upon component unmount?

Determine the console output order for the provided code with `setTimeout`, `Promise`, and synchronous `console.log`, explaining it through the Event Loop.

If you assign `state.userName = 'Max'`, will the content of `h1` change?

If you create a `setInterval` or add an event listener to `window` inside `setup`, will they be automatically removed upon component unmount?

Imagine a queue of macro tasks with five `setTimeout` calls, and microtasks infinitely adding new microtasks, for example through recursive `Promise.resolve().then()`. What will happen to the interface and will these five timeouts ever execute? Why?

The user quickly types in the search field. What is the difference between `debounce`, `throttle`, and `AbortController` from a UX and network/backend load perspective? Which is better for live search?

Implement a `debounce` function that supports immediate invocation at the start of a series of events (`leading`), a trailing invocation at the end of the series by default, and a `debounceFunc.cancel()` method to cancel the scheduled call.

TypeScript: implement a `SnakeCase` type that deeply transforms object keys from `camelCase` to `snake_case`, maintaining type safety.

What and how many times will be logged to the console when clicking the button in the provided Vue code?

Implement a simplified `reactive(object)` function that mimics Vue 3: when reading a property, call `track(target, key)`, and when changing a property, call `trigger(target, key)`.

What is prototype pollution vulnerability?