Daily micro-tips for C#, SQL, performance, and scalable backend engineering.
Frameworks like Vue use Proxy for reactivity. You can too – update UI automatically when data changes. Basic Reactive Object: const data = { count: 0, name: ‘John’ }; const reactive = new Proxy(data, { set(target, property, value) { target[property] = value; // Update UI automatically document.getElementById(property).textContent = value; console.log(`${property} changed to ${value}`); return true; […]
Canceling multiple fetch requests individually is messy. One AbortController can cancel them all. Single Controller for Multiple Requests: const controller = new AbortController(); const signal = controller.signal; // Multiple requests with same signal const userRequest = fetch(‘/api/user’, { signal }); const ordersRequest = fetch(‘/api/orders’, { signal }); const settingsRequest = fetch(‘/api/settings’, { signal }); // […]
|| operator treats 0 and ” as falsy. ?? only checks null/undefined. Problem with ||: const count = 0; const display = count || 10; // Returns 10 (wrong!) // 0 is falsy, so falls back to 10 Solution with ??: const count = 0; const display = count ?? 10; // Returns 0 (correct!) […]
Replacing all occurrences with regex is overkill. replaceAll() is simpler and more readable. Old Regex Way: const text = “Hello World, Hello Universe”; const result = text.replace(/Hello/g, “Hi”); // “Hi World, Hi Universe” // Easy to mess up – forget ‘g’ flag and only first is replaced! New replaceAll() Way: const text = “Hello World, […]
JSON.parse(JSON.stringify()) is clunky and breaks on Dates/Functions. Use structuredClone() instead. Old Unreliable Way: const original = { name: ‘John’, date: new Date() }; const copy = JSON.parse(JSON.stringify(original)); console.log(copy.date); // String, not Date! ❌ New Built-In Way: const original = { name: ‘John’, date: new Date(), nested: { deep: { value: 42 } } }; const […]
Getting last array element with arr[arr.length – 1] is verbose. Use .at() instead. Old Way: const arr = [10, 20, 30, 40, 50]; const last = arr[arr.length – 1]; // 50 const secondLast = arr[arr.length – 2]; // 40 New Way: const last = arr.at(-1); // 50 const secondLast = arr.at(-2); // 40 const first […]
Single Page Applications leaking memory from unfinished fetch requests? AbortController is your solution to clean up abandoned API calls. The Memory Leak Problem: // Common React/Vue pattern causing leaks async function fetchUserData(userId) { const response = await fetch(`/api/users/${userId}`); const data = await response.json(); setUserData(data); // State update } // User clicks between tabs quickly: // […]
Your app crashes with “Cannot read property ‘name’ of undefined”? Optional chaining (?.) safely accesses nested properties without try-catch blocks. The Error-Prone Old Way: const user = getUserData(); // Might return null // ❌ This crashes if user is null/undefined const name = user.profile.name; // TypeError: Cannot read property ‘profile’ of undefined // ❌ Traditional […]
Your AJAX calls fail randomly due to network hiccups or server load? Implement smart retry logic that actually works. The Problem with Basic Retry: // Bad: Immediate retry can make things worse function badRetry(url, maxAttempts) { for (let i = 0; i < maxAttempts; i++) { try { return await fetch(url); } catch (error) { […]
Search inputs lagging? Scroll events killing performance? Understanding debounce vs throttle is critical for responsive UIs. Debounce – Wait Until User Stops: function debounce(func, delay) { let timeoutId; return function(…args) { clearTimeout(timeoutId); timeoutId = setTimeout(() => { func.apply(this, args); }, delay); }; } // Usage: Search input const searchInput = document.getElementById(‘search’); const performSearch = debounce((query) […]
This is NOT about micro-optimizations.It’s about callback overhead. Example items.forEach(item => process(item)); vs for (let i = 0; i < items.length; i++) { process(items[i]); } Why forEach creates a function call per iteration Harder for JS engines to optimize No early break support When it matters Large arrays Hot paths Real-time processing Rule Readability first.But […]
Works locally. Fails in production. Hidden issue Browsers limit parallel connections per origin. Fix Batch requests Use request queues Prefer a single endpoint await Promise.allSettled(requests); Why Uncontrolled parallelism = dropped requests.
This bug survives code reviews way too often. Problem forEach does not await async callbacks. items.forEach(async item => { await save(item); }); This exits immediately. Errors may never surface. Correct for (const item of items) { await save(item); } Why it matters Async flow control must be explicit, not assumed.
AJAX requests stall… server logs show nothing. Hidden reason Browsers limit parallel connections per origin (usually 6). When it happens Long-polling Hanging fetch calls Images + API calls from same domain Fix Abort unused requests Use AbortController const controller = new AbortController(); fetch(url, { signal: controller.signal }); // later controller.abort();
Many developers assume setTimeout(fn, 0) runs instantly.It never does. Why JavaScript has a single-threaded event loop setTimeout callbacks go to the macrotask queue Rendering, promises, microtasks run first console.log(‘A’); setTimeout(() => console.log(‘B’), 0); Promise.resolve().then(() => console.log(‘C’)); console.log(‘D’); Output A D C B Impact Race conditions UI glitches Unexpected async order Fix Use microtasks when order […]
$.ajax({ timeout: 5000 }); Why it mattersPrevents hanging UI states.
const copy = structuredClone(obj); Why it mattersHandles Dates, Maps, Sets safely.
let timeout; input.oninput = () => { clearTimeout(timeout); timeout = setTimeout(sendRequest, 300); }; Why it mattersLess load, better UX.
const controller = new AbortController(); fetch(url, { signal: controller.signal }); controller.abort(); Why it mattersPrevents race conditions and wasted bandwidth.
fetch(url, { method: “POST”, headers: { “Content-Type”: “application/json” }, body: JSON.stringify(data) }); Why it mattersAvoids silent model binding failures.
requestIdleCallback(() => heavyWork()); Why it mattersRuns tasks without blocking UI.
Multiple rapid requests = stale UI updates. const controller = new AbortController(); fetch(url, { signal: controller.signal }); controller.abort(); Why this mattersPrevents outdated responses from overwriting newer state.
Why structuredClone() Beats JSON Deep Copy const copy = structuredClone(original); Why this mattersstructuredClone preserves complex types and avoids silent data corruption.
Returning pre-rendered HTML via Ajax can outperform JSON → DOM rebuild. fetch(‘/comments’) .then(r => r.text()) .then(html => container.innerHTML = html); Why this worksLess JS work, fewer reflows, simpler rendering.
Misusing these kills UX and performance. // Debounce: waits until user stops debounce(search, 300); // Throttle: runs at most once per interval throttle(scrollHandler, 200); Why it mattersSearch inputs want debounce. Scroll/resize want throttle.
Array.forEach() does not await async functions.This silently causes race conditions and partial execution. // ❌ This does NOT wait items.forEach(async item => { await process(item); }); // ✅ Correct for (const item of items) { await process(item); } Why this mattersforEach ignores promises. Errors get swallowed, execution order breaks.
Network OK, UI frozen. Why it happensState updated outside render cycle. Why it mattersUsers see stale data. Vital fix Centralize state updates.
No leaks visible. Why it happensDetached DOM references. Why it mattersLong sessions slow down. Vital fix Null references explicitly.
Intervals lose accuracy. Why it happenssetInterval stacks delays. Why it mattersAnimations and polling drift. Smart fixUse recursive setTimeout.
No crash, slow death. Why it happensDetached DOM references. Why it mattersLong-running apps degrade silently. Smart fixClear references on element removal. element = null;