Primitive and Non Primitive data types

1. Primitive Datatypes

Primitive types are the basic building blocks of JavaScript.
They are simple, immutable values — meaning they don’t hold references or complex structures.
Each primitive directly represents a single value.
Primitive types include:

• Number
• String
• Boolean
• Undefined
• Null
• BigInt
• Symbol

💡 F*un fact: *When you copy a primitive, you’re copying the actual value, not a reference.
Example:

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let a = 10;
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let b = a;  // b gets a copy of the value 10
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b = 20;
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console.log(a); // 10 (unchanged)

undefined vs null

💡 I**n short:

• undefined → “I haven’t been given a value yet.”
• null → “I’ve been deliberately emptied.”

Number vs BigInt

⚠️ Note: You can’t mix them directly.

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10n + 10; // ❌ TypeError

Symbol

A Symbol creates a unique, immutable identifier every time it’s called — even with the same description.

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Symbol('id') === Symbol('id'); // false

Used for hidden or private object keys that don’t appear in normal enumeration.

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const meta = Symbol('meta');
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const user = { name: 'Alice' };
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user[meta] = { lastUpdated: 'today' };
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console.log(Object.keys(user)); // ['name']
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console.log(user[meta]);        // { lastUpdated: 'today' }

2. Non-Primitive Datatypes

Non-primitive types are also known as reference types because they don’t store the actual value — they store a reference to where the value lives in memory.
They can hold complex structures and collections of data.
They’re more flexible and can store multiple values under one variable.
Non-primitive types include:

• Object
• Array (which is actually a special kind of object)

💡 R*emember: *When you copy or compare non-primitives, you’re dealing with references, not values.
Two objects with identical content are not equal because they live in different memory locations.
Example:

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let user1 = { name: "Alice" };
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let user2 = user1; // both point to the same memory reference
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user2.name = "Bob";
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console.log(user1.name); // "Bob" (because they share the same reference)

In short: