2.1.26 [ECMA-262/5] Section 126.96.36.199, Array.prototype.forEach ( callbackfn [ , thisArg ] )
The specification states:
NOTE The forEach function is intentionally generic; it does not require that its this value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method. Whether the forEach function can be applied successfully to a host object is implementation-dependent.
IE9 Mode, IE10 Mode, and IE11 Mode (All Versions)
The forEach method can be applied to a host object; however, some host objects may reject such an application.