What's the point of parameters in a function?

Nicholas Lee

Actually, you don't have to list parameters in the function. Every JavaScript function receives it's own arguments variable. This is an array containing all of the arguments passed to the function. You can access each argument using array notation:

function add() {
  var results = 0; 
  for (var i = 0; i < arguments.length; i++) {
    results += arguments[i];
   }
 return results;
}

add(1,2,3); // returns 6

I'm not entirely sure I understand your question fully, but let me try to explain.

When defining a function, you must name the parameters to be able to refer to them inside the function in a readable manner.

function addTwoNumbers(a, b) {
   return a + b;
}

While this function could be written like this:

function addTwoNumbers() {
   return arguments[0] + arguments[1];
}

It's hardly readable, and anyone using your function wouldn't be able to tell how many parameters your function expects and what they should be.

Consider a slightly more complex scenario:

function greetMe(yourName, yourJob) {
   return "Hello, " + yourName + ". I've heard you are a " + yourJob + ".";
}

If you were to use the arguments Array-like object here, the code would be much harder to read.

Unnamed function parameters become a huge problem as your function grows more complex, and you do more things with them. If your function accepted 10 parameters, it would be extremely hard to track the position of each parameter to figure out what that parameter is.

Functions in all programming languages are modelled after mathematical functions, which turn a number of inputs (parameters) into an output (return value).

Bottom line, if you don't name your function parameters, other people (and even yourself) won't know how many of them there are and what they represent, and you'll have to resort to using the arguments Array-like object to reference them inside the function, and actually do things with them.