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Explain server.ts and main.ts in Angular Universal
Server.ts SSRs initial HTML via Node/Express; main.ts bootstraps the browser app and hydrates the DOM. First request hits the server; later navigations are client-side only.
How do you create a POST API endpoint in SvelteKit?
Add a +server.js file in a src/routes subdirectory, export a POST handler returning a Response, and note that +server files never run in the browser.
What is the purpose of +page.server.js in SvelteKit?
Exclusively server-side load feeding the data prop, used for secrets like DB queries and private env vars.
What is SSR and what are its advantages over a client-side SPA?
This tests server-client rendering trade-offs. A strong answer defines SSR as server HTML generation plus client hydration, citing faster time-to-content, better SEO for async data, and unified component logic.
Explain patch flags and static hoisting in Vue 3's compiler
Tests your grasp of compiler-informed virtual DOM optimizations. A strong answer covers patch flags as bitmap hints for dynamic bindings and static hoisting as extracting static nodes to skip diffing. Red flag: claiming Vue 3 removes the virtual DOM.
How does Svelte compile count += 1 into DOM updates?
Tests if you know Svelte reactivity is compile-time via runes, not runtime proxies. Good answer: $state marks reactive vars; runes are compiler hooks; compiler emits DOM-sync code. Red flag: describing useState or VDOM.
Compare Angular Zone.js and Vue 3 Proxy reactivity
This tests update granularity. Contrast Vue 3 Proxy tracking, targeting only affected components, with Angular Zone.js patching async APIs to trigger top-down dirty checking across tree. Vue binds deps at render; Angular compares values each cycle.
How is a Vue template compiled into a render function?
Map v-if to ternaries, v-for to array map, and events to onXxx props.
Why is Svelte called a 'disappearing framework'?
Tests whether you understand compile-time versus runtime-heavy frameworks. A strong answer says Svelte compiles components to vanilla JS at build time, shipping a tiny runtime instead of a reconciler or virtual DOM. Red flag: claiming there is zero runtime.
What is the Virtual DOM's role during a Vue state update?
Tests your grasp of Vue's reactive render pipeline. A strong answer: state change triggers a new virtual DOM tree; runtime diffs it against the old tree to apply only necessary real DOM updates. Red flag: saying virtual DOM updates browser DOM directly.
How would you diagnose and optimize slow Angular component tests?
Tests Angular test economics and runner overhead. Strong answers profile with Vitest, swap Karma for jsdom/happy-dom, mock services, and reduce TestBed recompilation via targeted imports.
Describe the role of a spy in testing with a framework example
This tests whether you know a spy records calls without replacing original implementation. A strong answer defines the tracking role, picks a concrete Vue or Angular handler, and asserts with toHaveBeenCalled.
How do you test a Svelte component updates a writable store?
Import the store with the component, render, await fireEvent.click, then assert the store value.
How do you mock an async service call in an Angular component test?
This tests Angular unit isolation and HTTP mocking. A strong answer covers HttpTestingController setup, flushing a mock response, asserting UI changes, and notes mocking avoids flaky networks. Red flag: using real HTTP calls in unit tests.
How do you test emitted events using Vue Test Utils?
Tests Vue Test Utils event inspection. Strong answer: mount, trigger('click'), then check wrapper.emitted('increment') for the payload array. Remember it returns an array of arrays, one per emission.
What is Angular's TestBed and when would you use it?
Say createComponent returns a fixture with no immediate binding, so await fixture.whenStable before asserting DOM.
What is the fundamental difference between unit and component tests?
Isolation levels in frontend testing. Unit tests verify single functions or composables with mocked dependencies; component tests verify mounting, rendering, and interaction and pull in more code.
How do you architect Svelte stores to minimize WebSocket re-renders?
Tests Svelte store granularity and subscription semantics. A great answer splits the monolith into domain stores, uses derived selectors to isolate slices, and leverages readable stores to encapsulate the WebSocket source.
Implement virtual scrolling for a large list in Vue
Tests DOM cost awareness and viewport culling. Strong answer: mount only visible nodes plus overscan, recycle DOM on scroll, and preserve total scroll height with a spacer. Red flag: suggesting pagination or naive v-for without keys.
How does Svelte surgically update the DOM without VDOM?
Tests VDOM overhead vs compile-time optimization. A strong answer explains that Svelte compiles reactive dependencies into direct DOM API calls, skipping tree creation and diffing. Red flag: claiming VDOM is slow because the DOM itself is slow.