What happens if I don't pass a parameter in a Javascript function?

Question

I am new to the world of Javascript and am tinkering with writing very basic functions and stumbled upon the example below by accident and am unsure why it works when I am not passing a parameter when the function demands it.

Sample function

function myfunction(x) {     alert("This is a sample alert"); } 

Now if I call the function myfunction(); I am presented with the alert. Why is that that I am able to call the function without any errors or warnings when I have not passed a parameter?

EDIT

I did not expect so many great answers and I am by no means in a position yet able to say which answer is the best so am I able to request people to suggest the best answer and I'll award the acceptance to that person.

Answer 1

Nothing will happen- meaning you won't get an error or a warning as passing the parameters in javascript is optional.
All the parameters that weren't "supplied" will have the undefined value.

function foo(x, y, z){     //... }  foo(1); 

Inside the foo function now:

function foo(x, y, z){     x === 1     y === undefined     z === undefined } 

You can even pass more arguments, like:

foo(1,2,3,4,5,7); // Valid! 

You can know the amounts of parameters supplied by arguments.length from inside the function.

function foo(x, y, z) {      console.log('x value: ' + x);      console.log('y value: ' + y);      console.log('z value: ' + z);      console.log('Arguments length: ' + arguments.length);  }  console.log('Zero parameters');  foo();  console.log('Four parameters');  foo(1, 2, 3, 4);

Example of useful function that handle any amount of parameters:

function max() {      var maxValue = arguments[0];      for (var i = 1; i < arguments.length; i++) {          if (maxValue < arguments[i]) {              maxValue = arguments[i];          }      }      return maxValue;  }    alert(max(1, 5, 7, 2, 88, 32, 44));