add call stack

Author: brijeshkumar-chavda

javascript_under_the_hood/call_stack.md

@@ -0,0 +1,50 @@
+# Call Stack
+
+What
+
+- A callback is a function that is passed as an argument to another function. It's a way to defer the execution of a function until a certain event occurs or a condition is met.
+
+Why
+
+- Function Calls: Keeps track of the order of function calls and their return addresses.
+- Execution Context: Stores information about each function call, including local variables, arguments, and the return address.
+
+How
+
+- Function Call: When a function is called, its execution context is pushed onto the call stack.
+- Execution: The function's code is executed.
+- Return: When the function returns, its execution context is popped off the stack, and the returned value is passed back to the calling function.
+
+Example
+
+```javascript
+function greet(name) {
+  console.log("Hello, " + name + "!");
+}
+
+function main() {
+  greet("Alice");
+  console.log("Main function finished.");
+}
+
+main();
+```
+
+Call Stack:
+
+- main function is called.
+- main's execution context is pushed onto the stack.
+- greet is called within main.
+- greet's execution context is pushed onto the stack.
+- greet executes and returns.
+- greet's execution context is popped off the stack.
+- main continues execution.
+- main's execution context is popped off the stack.
+
+Note
+
+- The call stack plays a crucial role in managing the flow of execution in JavaScript. Understanding the call stack is essential for debugging and understanding how functions are called and return values.
+
+Analogy
+
+- Think of the call stack as a stack of plates. The most recently added plate is the top plate, and it's the first one to be removed when you need a plate. Similarly, in JavaScript, the most recent function call is at the top of the stack, and it's the first one to be removed when the function returns.

javascript_under_the_hood/javascript_engine.md

@@ -10,6 +10,13 @@ Why
 - Optimizes performance: Employs techniques like Just-In-Time (JIT) compilation to improve execution speed.
 - Manages memory: Handles memory allocation and garbage collection.
 
+How
+
+- Parsing: Breaks down JavaScript code into smaller parts (tokens).
+- Abstract Syntax Tree (AST): Creates a tree-like structure representing the code's structure.
+- Interpretation or Compilation: Executes code directly or compiles it into machine code.
+- Execution: Runs the compiled code or interpreted instructions.
+
 Example
 
 - V8: Used in Google Chrome and Node.js.