javascript-var-forgetting-var.js

(function() {
  myVar = 1;
  console.log("myVar should be 1: " + myVar); // should be 1
  setTimeout(function() {
    console.log("myVar should be 1, but isn't: " + myVar); // should be 1, but isn't 
  }, 100);
})();

(function() {
  myVar = 2;
})();

console.log(myVar); 

javascript-var-scope.js

(function() {
  console.log(myVar); // undefined
  var myVar = 1;
  console.log(myVar); // OK
  (function() {
    console.log(myVar); // OK
  })(); 
})();

console.log(myVar); // Ref Error: myVar not defined

(function() {
  for(var myVar1 = 1; myVar1 < 2; myVar1++) {
    console.log(myVar1); // OK
  }
  console.log(myVar1); // It's still HERE !
})();