2.1.29 [ECMA-262/5] Section, Array.prototype.reduce ( callbackfn [ , initialValue ] )


The specification states:

 NOTE The reduce 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 reduce function can be applied successfully to a host object is implementation-dependent.

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The reduce method can be applied to a host object; however, some host objects may reject such an application.