In JavaScript, stack and heap memory are two areas where the language manages memory for variables and data during the execution of a program. Understanding these concepts helps clarify how JavaScript handles data storage, memory allocation, and garbage collection.

Stack Memory:

• Definition: A stack is a memory structure used to store primitive values and the execution context of function calls (e.g., local variables, function arguments).
• Structure: Works on a LIFO (Last In, First Out) basis. The last item added is the first to be removed.
• Usage:
  • Stores primitive data types: undefined, null, boolean, number, bigint, string, and symbol.
  • Holds references to objects stored in the heap.

Key Characteristics:

1. Fast access: Memory allocation and deallocation in the stack are quick because of its linear structure.
2. Limited size: Stack memory is typically smaller and limited compared to heap memory.
3. Temporary storage: Data is cleared when the function execution is complete or the variable goes out of scope.

Example:

function add(a, b) {
  let sum = a + b; // `a`, `b`, and `sum` are stored in the stack.
  return sum;
}
add(3, 4);

Heap Memory:

• Definition: The heap is a larger memory area used for storing objects and reference types.
• Structure: Unlike the stack, it is not ordered and allows dynamic memory allocation.
• Usage:
  • Stores reference data types, such as objects, arrays, and functions.

Key Characteristics:

1. Dynamic allocation: Memory is allocated and managed dynamically as needed during runtime.
2. Garbage collection: The JavaScript engine (e.g., V8 in Chrome) automatically clears unused objects in the heap via garbage collection.