Javascript add extra argument

Question

Lets take a look at this code:

var mainFunction = function() {
  altFunction.apply(null, arguments);
}

The arguments that are passed to \"mainF

Answer 1

var mainFunction = function() {
    var args = [].slice.call( arguments ); //Convert to array
    args.push( "extra data");
    return altFunction.apply( this, args );
}