JavaScript

Core JavaScript patterns, async behaviour, and array/object manipulation.

15 articles

• Fix Hydration Failed Errors in Next.js

  Fix Next.js hydration mismatch errors by matching server and first client output, debugging dates, storage, invalid HTML, CSS, CDN, and production-only changes.

  July 28, 2026

• Fix npm ERESOLVE Dependency Tree Errors

  Fix npm ERR! ERESOLVE dependency tree errors by reading peer conflicts, aligning package versions, using overrides safely, and keeping CI installs reproducible.

  July 27, 2026

• JavaScript Algorithm Interview Problems: 8 Patterns with Solutions

  Learn eight JavaScript algorithm interview patterns with worked solutions: array transforms, hashing, interval scans, matrix rotation, and async sequencing.

  July 21, 2026

• React 19 Features for Interviews: Actions, use(), the Compiler, useOptimistic & ref-as-prop

  The React 19 features interviewers actually ask about — Actions with useActionState/useFormStatus, the use() hook, the React Compiler's automatic memoization, useOptimistic, ref as a prop (no more forwardRef), and native document metadata — with correct, runnable code.

  March 20, 2024

• Debouncing in React 19: Correct Hooks, useDeferredValue, and Cancelling Stale Requests

  How to debounce user input in React 19 the right way — a correct reusable useDebouncedValue hook, when to reach for useDeferredValue/useTransition instead, and how to cancel stale in-flight requests with AbortController.

  March 20, 2024

• Two-Way Binding in React: A Typed useBind Hook (and When to Use React 19 Actions Instead)

  React has no built-in two-way binding like Angular's ngModel. Build a correct, fully-typed useBind hook that handles text, number and checkbox inputs — and learn when uncontrolled inputs or React 19 form Actions are the better choice.

  December 18, 2023

• Creating a Custom Alert in React with TypeScript

  Here's a custom alert component without using any external libraries, just using React and TypeScript.

  July 25, 2023

• Fix: Refused to set unsafe header Origin (XMLHttpRequest)

  Origin is a forbidden header — browsers set it and silently refuse setRequestHeader overrides. Why the restriction exists and the server-side CORS fix.

  October 11, 2022

• Sequential Promise using reduce method.

  Resolve multiple promises in sequence and return a promise using reduce method

  September 27, 2022

• Given a set of distinct integers array, return all possible subsets.

  Given a set of distinct integers array ```myArray```, return all possible subsets (the power set).

  September 25, 2022

• Missing Number In An Array

  Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.

  September 24, 2022

• How to Square numbers in Array

  should return square array.

  September 15, 2022

• Truth Check using Javascript

  Check if the predicate (second argument) is truthy on all elements of a collection (first argument).

  September 14, 2022

• Merge Intervals using Javascript

  Given a collection of intervals, merge all overlapping intervals.

  June 14, 2021

• Group Anagrams in JavaScript: Two Approaches (Sorted Key vs O(n·k) Count Key)

  Group anagrams in JavaScript two ways: a sorted-string hash key (O(n·k log k)) and the optimal character-count key (O(n·k)). Clean code, complexity analysis, and the interview follow-ups.

  May 22, 2021

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