[javascript] How do I call a function inside of another function?

I just want to know how to call a javascript function inside another function. If I have the code below, how do I call the second function inside the first?

function function_one()
{
alert("The function called 'function_one' has been called.")
//Here I would like to call function_two.
}

function function_two()
{
alert("The function called 'function_two' has been called.")
}

function function_one() {
  function_two(); 
}

function function_two() {
//enter code here
}