scoping.js

function doSomething() {
  if(true) {
    let booleanValue = true;
  }
  
  console.log(booleanValue); // It'll throw an exception in the compiler because booleanValue doesn't exist out here.
}

function doSomething() {
  if(true) {
    var booleanValue = true;
  }
  
  console.log(booleanValue); // comes out true. booleanValue got escalated up to being inside of doSomething() and not instead of the if() statement
}