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

Update 2016: You must convert the arguments to an array before adding the element. In addition to the slice method mentioned in many posts:

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

You can also use the Array.from() method or the spread operator to convert arguments to a real Array:

var args = Array.from(arguments);

or

var args = [...arguments];

The above may not be optimized by your javascript engine, it has been suggested by the MDN the following may be optimized:

var args = (arguments.length === 1 ? [arguments[0]] : Array.apply(null, arguments));

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments