25 Things JavaScript Developers Should Know, but Probably Don't - JavaScript Proxies: The Most Powerful Feature You’re Not Using

🔥 Episode 22 of “25 Things JavaScript Developers Should Know (But Probably Don’t)” The JavaScript Tool I'm using to demonstrate: https://runjs.app/ColorCode ColorCode Etsy Merchandise store: https://www.etsy.com/shop/ColorCodeStore 📌 Description JavaScript Proxies let you intercept, validate, and control objects in real time, and almost nobody is using them properly. In this episode of 25 Things JavaScript Developers Should Know (But Probably Don’t), we dive deep into JavaScript Proxies and show how they let you: Block invalid data (like negative ages 👀) Protect sensitive fields like passwords Create virtual & computed properties Debug who is reading your state Intercept function calls Build runtime guardrails without TypeScript This is the same technology behind Vue 3’s reactivity system, powerful state managers, and modern JavaScript frameworks — and you can use it today with plain JS. No slides. No fluff. Just code and practical patterns you can use immediately. 🧠 What you’ll learn What a JavaScript Proxy actually is How Proxy traps (get, set, apply) work How to prevent bad writes at runtime How to block reads to sensitive fields How to create computed properties on plain objects How to debug mysterious state access How Reflect fits into all of this ⚠️ Important note Client-side proxies are not security. The server must still enforce real rules. But Proxies are incredible for correctness, debugging, and developer safety. 🧩 Timestamps 00:00 – Intro (you can't be -5 years old) 01:05 – What is a Proxy? 02:00 – 1 - Basic Intercept 06:30 – 2 - Protect Props 08:28 – 3 - Sanitize Writes 10:43 – 4 - Auto-fallback (defaults) 11:35 – 5 - Conditional read-only 12:15 – 6 - Virtual & Dynamic props 17:35 – 7 - Validate Function calls 16:20 – Reflect API 21:16 – Warnings! 28:00 – Outro 🔥 Series This is Episode 22 of “25 Things JavaScript Developers Should Know (But Probably Don’t)” More coming soon. 🧪 Try this yourself Wrap an object in a Proxy and ask: “What rules should this object enforce?” That’s where things get powerful.