The chief factor in determining which islands of the Indonesian Archipelago are Asian has been the location of the colonial possessions of the various empires there (not all European).
ðə tʃˈiːf fˈæktɚɹ ɪn dɪtˈɜːmɪnɪŋ wˌɪtʃ ˈaɪləndz ʌvðɪ ɪndoʊnˈiːʒən ˌɑːɹkɪpɪlˈeɪɡoʊ ɑːɹ ˈeɪʒən hˈæzbiːn ðə loʊkˈeɪʃən ʌvðə kəlˈoʊnɪəl pəzˈɛʃənz ʌvðə vˈɛɹiəs ˈɛmpaɪɚz ðɛɹ nˌɑːt ˈɔːl jˌʊɹɹəpˈiən.