🚨 Java & JavaScript Are NOT Call by Reference

This is one of those concepts that seems obvious… until it breaks your code.

Many developers believe:

“Objects are passed by reference in Java or JavaScript”

❌ That’s incorrect.

👉 Both Java and JavaScript are strictly call by value

🧠 Why This Feels Wrong

If you’ve ever done this:

function update(user):
    user.name = "Ishwar"

…and seen the change reflected outside,
it feels like pass by reference.

But then this:

function reset(user):
    user = new Object()

Does nothing to the original.

So what’s really going on?

⚙️ What’s Actually Happening

• Variables store values
• For objects → that value is a reference (memory address)

👉 When calling a function:

• A copy of that value is passed
• Not the original variable

🔍 The Key Insight

Inside the function:

• You get a copy of the reference
• Both point to the same object → mutation works
• But reassignment only affects the local copy

🔁 Mental Model

original variable → copy value → function parameter

👉 You never get direct access to the original variable

📦 Stack vs Heap (Quick View)

• Stack → variables (copies live here)
• Heap → actual objects

👉 You copy the reference value, not the object

🌍 Applies Beyond Just Java

💡 Final Takeaway

Everything is pass by value.
Some values just happen to be references.

🚀 Why This Matters

This concept shows up in real-world bugs:

• Unexpected object mutations
• State issues in frontend apps
• Backend data inconsistencies
• API transformation bugs

🤔 Discussion

When did this finally click for you?

• Early learning phase
• On the job
• Or after debugging something painful 😅

Built for devs who like understanding why, not just what.
More deep dives coming.