Is it bad to pass more arguments than the function declares? [closed]

Question

I have a function

function callback(obj){...} 

Is it okay to pass in more objects than were declared in the function signature? e.g. call it like this:

callback(theObject, extraParam); 

I tried it out on Firefox and it didn't seem to have a problem, but is it bad to do this?

Answer 1

JavaScript allows this, you can pass any arbitrary number of arguments to a function.

They are accessible in the arguments object which is an array-like object that has numeric properties containing the values of the arguments that were used when the function was invoked, a length property that tells you how many arguments have been used on the invocation also, and a callee property which is a reference to the function itself, for example you could write:

function sum(/*arg1, arg2, ... , argN  */) { // no arguments defined   var i, result = 0;   for (i = 0; i < arguments.length; i++) {     result += arguments[i];   }   return result; } sum(1, 2, 3, 4); // 10 

The arguments object may look like an array, but it is a plain object, that inherits from Object.prototype, but if you want to use Array methods on it, you can invoke them directly from the Array.prototype, for example, a common pattern to get a real array is to use the Array slice method:

function test () {   var args = Array.prototype.slice.call(arguments);   return args.join(" "); } test("hello", "world"); // "hello world" 

Also, you can know how many arguments a function expects, using the length property of the function object:

function test (one, two, three) {   // ... } test.length; // 3