Question

I need a method that can have an arbitrary number of parameters. In C# we have the params statement. Do we have anything similar in JavaScript?

Answer 1

There is the arguments collection, which contains all arguments passed to the function.

There is a) no need to specify “optional” arguments in the function signature and b) any function accepts any number of parameters.

function foo() {
  console.log(arguments);
}

foo(1,2,3,4);  // logs [1, 2, 3, 4]

Likewise, there is no need to supply “required” arguments in a function call:

function foo(a, b, c, d) {
  console.log(arguments);
}

foo(1,2);  // logs [1, 2]

Any argument named in the signature but not supplied in the function call will be undefined.

Note that arguments behaves like an Array, but technically it isn’t one. For example, you can call arguments[0], but you can’t call arguments.slice(). What you can do to get around this is using the Array prototype:

Array.prototype.slice.call(arguments, 1, 2);

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The so-called rest parameter ... is a new (ES6+) addition to the language and makes working with variadic functions more comfortable. @ArunCM’s answer explains it.