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Shanthi's Dev Diary
Shanthi's Dev Diary

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structuredClone() — The Deep Copy Hero JavaScript Deserved 🦸‍♀️

#javascript #webdev #react #node

Let’s be honest.

Every JavaScript developer has broken production at least once because of copying objects the wrong way.

You thought you cloned it.

JavaScript smiled.

Then changed the original too.

Enter structuredClone() — the native deep-cloning superhero that finally says:

“Relax. I got this.”

The Problem: “Why did my original object change?! 😭”

Classic situation:

const user = {
  name: "Shanthi",
  skills: ["JavaScript", "React"]
};

const copy = user;
copy.skills.push("TypeScript");

console.log(user.skills);
// ["JavaScript", "React", "TypeScript"] 😱
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You didn’t mean to update the original…

JavaScript just assumed you were feeling adventurous.

The Old (Painful) Way 😬

We all tried this at some point:

JSON.parse(JSON.stringify(obj))
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It looks clever.

It feels clever.

But it betrays you silently.

What it breaks:

  • ❌ Date becomes a string
  • ❌ Map, Set vanish into thin air
  • ❌ undefined, NaN, Infinity disappear
  • ❌ Circular references? App crash 💥

Basically, it copies your data and forgets its personality.

Meet structuredClone() 🧠✨

JavaScript finally said:

“Okay fine, here’s a proper deep clone.”

const cloned = structuredClone(original);
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That’s it.

No imports.

No libraries.

No emotional damage.

What Makes structuredClone So Cool?

✅ It actually understands JavaScript data.

It supports:

  • Objects & Arrays
  • Date
  • Map, Set
  • RegExp
  • BigInt
  • TypedArrays
  • Circular references (YES 🔥)

Basically, real-world data. Not just JSON-shaped dreams.

Example: Deep Clone That Actually Works 

const user = {
  name: "Shanthi",
  meta: {
    joined: new Date(),
  },
};

const clone = structuredClone(user);

clone.meta.joined.setFullYear(2030);

console.log(user.meta.joined.getFullYear());
// Still 2024 😌
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No side effects.

No surprises.

No apology messages to your team.

Circular References? Bring It On 💪 

const obj = {};
obj.self = obj;

const cloned = structuredClone(obj);

console.log(cloned.self === cloned); // true
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Old methods would:

  • ❌ Cry
  • ❌ Throw errors
  • ❌ Give up on life

structuredClone just nods politely and continues.

Map & Set — Finally Respected 🫶 

const data = {
  map: new Map([["a", 1]]),
  set: new Set([1, 2, 3]),
};

const clone = structuredClone(data);

clone.map.set("b", 2);

console.log(data.map.has("b")); // false 🎉
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Your original data remains unbothered.

What It Won’t Clone (And That’s Fair)

Some things simply refuse to be cloned:

  • ❌ Functions (they have commitment issues)
  • ❌ DOM nodes (use cloneNode)
  • ❌ Symbols
  • ❌ WeakMap, WeakSet

Try cloning these and JavaScript will politely throw a DataCloneError instead of silently ruining your data.

Honestly? We appreciate the honesty.

structuredClone vs Spread Operator 🥊 

const original = { a: { b: 1 } };

const shallow = { ...original };
const deep = structuredClone(original);

shallow.a.b = 2;

console.log(original.a.b); // 2 ❌
deep.a.b = 3;
console.log(original.a.b); // still 2 ✅
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Spread operator:

“I’ll copy the top layer and hope for the best.”

structuredClone:

“I’ll copy everything. Thoroughly.”

Performance: Should I Worry?

  • Faster than JSON.parse(JSON.stringify())
  • Optimized by modern JS engines
  • Safe for state cloning and message passing

⚠️ Just don’t clone massive objects in tight loops unless you enjoy performance reviews.

Where You’ll Actually Use This

  • React state updates (immutability without headaches)
  • Redux / Zustand / any state manager
  • Web Workers
  • Undo / redo features
  • Caching snapshots
  • “Why did this mutate?” bug prevention

Browser & Runtime Support 🌍

Good news:

  • Modern browsers ✅
  • Node.js 17+ ✅
  • Deno, Bun ✅

No polyfills. No drama.

Final Thoughts 💭

structuredClone() is:

  • ✅ Native
  • ✅ Safe
  • ✅ Deep
  • ✅ Honest about errors

If you’re still using JSON.parse(JSON.stringify()), it’s okay.

We all grow. 😄

Modern JavaScript has given us a proper deep clone.

Let’s actually use it.

💬 Have you been betrayed by shallow copies before?

Share your cloning horror stories in the comments!

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