Javascript: “Infinite” parameters for function?

Functions can access an array-like object called arguments that contains all the arguments that they received

function print_my_arguments(/**/){
    var args = arguments;
    for(var i=0; i<args.length; i++){
        console.log(args[i]);
    }
};

And you can do the opposite conversion (call a function given a list of arguments) with the apply method:

// These are equivalent:
print_my_arguments(1,2,3);
print_my_arguments.apply(null, [1,2,3]);

// The first parameter to `apply` is the `this`.
// It is used when the function is a method.
foo.bar(1,2,3);
var f = foo.bar; f.apply(foo, [1,2,3]);

Some important points to note:

1. arguments isn’t an actual array and it has none of the usual array methods (slice, join, etc). You can convert it to an array with the following line:

   var args = Array.prototype.slice.call(arguments);
   

2. Slice is also useful if you want your array to only contain the non-named arguments that were received:

   function foo(first_arg, second_arg /**/){
       var variadic_args = Array.prototype.slice.call(arguments, 2);
   }
   

3. Not every browser can handle an arbitrarily large number of function parameters. Last time I tested this, in Chrome and IE there was a stackoverflow after some 200.000 arguments. If your function can receive an arbitrarily large number of arguments, consider packing all of those arguments in an regular array instead.

4. Those /**/ comments that appear in the arguments lists for my examples are not mandatory. They are just a coding a convention that I use to mark my variadic functions and differentiate them from regular functions.

   // A quick glance would suggest that this function receives no
   // parameters but actually it is a variadic function that gets
   // its parameters via the `arguments` object.
   function foo(){
       console.log(arguments.length);
   }