Function arguments is an object; function arguments is not an array.

foo('bar')

Actual results: arguments instanceof Array = true

Expected results: arguments instanceof Array = false

Reference: ECMAScript-262 Language Specifications, Edition 3, 13 October 1999, Section 10.1.8: "The value of the internal [[Prototype]] property of the arguments object is the original Object prototype object, the one that is the initial value of Object.prototype"