Variables

• let
  • When value can be changed later (reassigned).
• const
  • Immutable (cannot be reassigned).
  • Must assign a value when declaring a const variable.
• var
  • Function-scoped.
  • Can lead to confusing and error-prone code.

// ✅ use const by default (var is not recommended)

let age =22// mutable
const name ="Hen"// immutable (most common)

Functions

• Use normal functions when:
  • You need your own this (object methods, constructors)
  • You need arguments
  • You want hoisting
• Use arrow functions when:
  • Writing short callbacks or inline functions
  • You want this to stay from the surrounding scope
  • You don’t need arguments or new

Normal function

function add (a, b) {
	return a + b
}

• this is dynamic (depends on how the function is called)

  const obj = {
    name: "Alex",
    greet: function () {
      console.log(this.name);
    }
  };
  
  obj.greet(); // "Alex"
  

• Can used as constructor

  function Person(name) {
    this.name = name;
  }
  
  const p = new Person("Alex"); // ✅ works
  

• Do NOT enforce parameter count (can pass any number of arguments)

  • will go into a special object called arguments.

  function sayHi() {
    console.log("hi");
  }
  
  sayHi(1, 2, 3, 4); // ✅ still works
  

Arrow function

const add = (a, b) => {
	return a + b
}