What will the following code output?

(function() {
  var a = b = 5;
})();

console.log(b);

The code above will output 5 even though it seems as if the variable was declared within a function and can’t be accessed outside of it. This is because

var a = b = 5;

is interpreted the following way:

var a = b;
b = 5;

But b is not declared anywhere in the function with var so it is set equal to 5 in the global scope.