t002-1.js

// file scope

console.log(a); // you may be surprised, but this works and logs undefined
                // this is because of the hoisting of definitions 
                // on top of the nearest function
var a = 1;
console.log(a);

function f1() { // f1 scope
  console.log(a); // this is ok -- functions have access to parent scope

  console.log(b); // works the same way as with 'a'
  var b = 1;
  console.log(b);

  // TODO: try uncomment
  // console.log(x);
  // this will throw an error: 'ReferenceError: x is not defined',
  // because x() defined in f2 scope
}

function f2() { // f2 scope
  console.log(x()); // hoisting help us here because 
                    // function definition is moved to the top of f2
  function x() {
    console.log('x');
  }
  console.log(x());

  // TODO: try uncomment
  // console.log(b);
  // this will throw an error: 'ReferenceError: b is not defined',
  // because 'b' defined in f1 scope
}

f1();
f2();