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Security notes, SOC lab write-ups and tested code by Mahir Faysal, a SOC Level 1 cybersecurity learner in Bangladesh, plus notes from my Next.js and Gemini projects. Sample posts are marked and drafts stay in the admin area.

All notes Coding tips · 168 Learning notes · 25 Practice · 1

Coding tips

null vs undefined in JavaScript: Differences, Checks and When to Use Each (Tested Examples)

null and undefined both mean "no value" in JavaScript, but they are not the same. Here are the real differences - typeof, == vs ===, default parameters, optional chaining, nullish coalescing and JSON - with output from Node.js 24.22.1.

November 7, 2026 · 11 min read · 10 views