Cannot Use Import Statement Outside a Module: ESM vs CommonJS
Fix SyntaxError: Cannot use import statement outside a module in Node and browsers: type module, .mjs, require of ESM and __dirname in ESM.
~8 min readread →
Work
Aditya has worked as a developer in Mumbai since 2016, about 10 years, mostly on enterprise web applications: Angular and React front ends, and Java and Spring Boot services behind them.
- Technical Lead, BNP Paribas May 2025 to nowAngular upgrades from v18 to v20, a shared component library and a React platform for SMS templates
- Full Stack Developer, Agiloft Dec 2024 to May 2025A Vue.js component monorepo and the gradual move of JSP pages to a single-page app
- Senior Software Engineer, HERE Technologies Sep 2022 to Dec 2024Map-based labelling tools in React and OpenLayers, and Spring Boot microservices
- Software Engineer, Adzapier Jun 2020 to Sep 2022IAB-certified consent management and Stripe billing
- Product Engineer, Moofwd Technologies Feb 2019 to May 2020Mastercard payment products (MPGS, SRC-I and MDES integrations)
- PHP Web Engineer, Trycatch Tech Oct 2016 to Feb 2019Laravel e-commerce and an Angular customer portal
Education: M.Sc. in Physics, Dr. Bhimrao Ambedkar University, Agra.
How Stacktrick is made
Stacktrick began as Aditya's personal blog on this domain (2021 to 2024) and relaunched in September 2026 as an interview-prep site. Drafts are prepared with AI tools. Aditya chooses the topics and reviews each guide before it is published; JavaScript, TypeScript and Python examples are run, Java and Angular examples are checked against the documentation, and every guide states the versions its code targets. The editorial policy explains the process and how to report a mistake.
A few guides to start with
All notes →React useEffect Cleanup: When It Runs and How to Avoid Leaks
When React runs useEffect cleanup, why Strict Mode mounts twice, and how to clean up listeners, timers, sockets and fetches without leaks.
~7 min readread →
Can't bind to 'ngModel' since it isn't a known property of 'input' in Angular
Fix Angular NG8002 Can't bind to 'ngModel' since it isn't a known property of 'input': import FormsModule, then fix formControl and inputs.
~7 min readread →
TypeScript TS2345: Not Assignable to Parameter of Type 'never'
Fix TS2345 'Argument of type string is not assignable to parameter of type never' from empty arrays, function unions and exhaustive checks.
~7 min readread →
ClassNotFoundException vs NoClassDefFoundError in Java
ClassNotFoundException vs NoClassDefFoundError in Java: what each error means, why classes go missing at runtime and how to fix the classpath.
~8 min readread →
Whitelabel Error Page 404 in Spring Boot: How to Fix It
Seeing the Whitelabel Error Page with status 404 in Spring Boot 3? Check the mapping, component scan, @RestController and context path.
~7 min readread →
Node.js Async Error Handling: Floating Promises and try/catch Gaps
Where async errors escape try/catch in Node.js, why a floating promise kills the process, and how to wrap causes and catch at one boundary.
~6 min readread →
SQL Null and Three-Valued Logic
NULL makes comparisons unknown, not false. See how that drops rows from WHERE, empties NOT IN and slips past CHECK constraints.
~6 min readread →
Docker 'Bind for 0.0.0.0:8080 failed: port is already allocated' Fix
Fix Docker 'port is already allocated' and 'address already in use': find the container or process on the port, then remap or bind to 127.0.0.1.
~8 min readread →
Git: failed to push some refs (fetch first, non-fast-forward)
Fix Git's error: failed to push some refs and ! [rejected] main -> main (fetch first): fetch, rebase or merge, and force-with-lease safely.
~7 min readread →
System Design: URL Shortener
Size a URL shortener from 100M links a month, pick between counter-based and random codes, and keep a 4,000 req/s redirect path cheap.
~7 min readread →
HTML Headings and Document Navigation
How screen reader users jump between headings, why levels should follow structure rather than font size, and how to fix skipped levels.
~6 min readread →
Cheat sheets
JavaScript Essentials
48 must-know facts & snippets
open & print →
TypeScriptFrom unknown to infer, on one page
open & print →
TypeScript Utility TypesPartial → Awaited, all of them
open & print →
ReactRendering to Server Components, on one page
open & print →
React HooksEvery hook, one example each
open & print →
AngularSignals to guards, standalone-first
open & print →
RxJS OperatorsThe 30 operators you'll actually use
open & print →
HTML & CSSSemantics to grid, cascade to stacking
open & print →
Node.jsEvent loop to streams, checked on Node 22
open & print →
JavaOOP to virtual threads, on one page
open & print →
Spring BootBeans to JWT and @Transactional, one page
open & print →
SQL & PostgreSQLJoins to MVCC, every query run on Postgres 16
open & print →
DockerDockerfile to Compose, layers to PID 1
open & print →
Git & CI/CDStaging area to canary deploys, on one page
open & print →
Data Structures & AlgorithmsBig-O to DP, with Python templates
open & print →
System DesignRendering to caching, plus five mini-designs
open & print →