ionelh

// Global execution context (not inside a function)
this === window // logs true

ionelh

foo; // 'bar'
window.foo; // 'bar'
this.foo; // 'bar'
(window.foo === foo && this.foo === foo && window.foo === this.foo) // true

ionelh

function a() {
  // some code
  b();
  // some more code
}

function b() {
  // some code
}

ionelh

function a() {
  // some code
  b();
  // some more code
}

function b() {
  // some code
}

ionelh

function a() {
  function b() {
    console.log(foo); // logs 'bar'
  }

  var foo = 'bar';
  b();
}

a();

ionelh

function a() {
  var foo = 'bar';
  b();
}

function b() {
  console.log(foo); // throws ReferenceError: foo is not defined
}

a();

ionelh

function a() {
  function b() {
    function c() {
      console.log(foo);
    }
    
    c();
  }
  
  var foo = 'bar';

ionelh

const myArrowFunction = () => {
  console.log(this === window);
};

class MyClass {
  constructor() {
    myArrowFunction();
  }
}

ionelh

class MyClass {
  constructor() {
    const myArrowFunction = () => {
      console.log(this === window);
    };
    myArrowFunction();
  }
}

var myClassInstance = new MyClass();

ionelh

function a() {
  // ...
}