var-let-diff.html

<script>
function compareLetVar() {
  // Using var
  console.log('Using var:');
  console.log(a); // Outputs: undefined (due to hoisting)
  var a = 5;
  console.log(a); // Outputs: 5

  if (true) {
      var b = 10; // Function-scoped
  }
  console.log(b); // Outputs: 10 (accessible outside the if block)

  // Using let
  console.log('\nUsing let:');
  // console.log(c); // ReferenceError: Cannot access 'c' before initialization
  let c = 15;
  console.log(c); // Outputs: 15

  if (true) {
      let d = 20; // Block-scoped
      console.log(d); // Outputs: 20 (accessible within the block)
  }
  // console.log(d); // ReferenceError: d is not defined

  // Re-declaration example
  var e = 25;
  var e = 30; // No error
  console.log(e); // Outputs: 30

  let f = 35;
  // let f = 40; // SyntaxError: Identifier 'f' has already been declared
  console.log(f); // Outputs: 35
}

compareLetVar();

</script>