ISO 3166-1 alpha-2 country code to country name conversion with a simple Javascript implementation, an array and a function. It completes the English version from https://gist.github.com/maephisto/9228207

[DEUTCH] Javascript ISO country code to country name mapping

//initially crawled from https://de.wikipedia.org/wiki/ISO-3166-1-Kodierliste
//2020-03-23, reviewed by @luwe1204 
isoCountries = {
    "AD": "Andorra",
    "AE": "Vereinigte Arabische Emirate",
    "AF": "Afghanistan",
    "AG": "Antigua und Barbuda",
    "AI": "Anguilla",
    "AL": "Albanien",
    "AM": "Armenien",
    "AN": "Niederländische Antillen (ehemalig)",
    "AO": "Angola",
    "AQ": "Antarktika",
    "AR": "Argentinien",
    "AS": "Amerikanisch-Samoa",
    "AT": "Österreich",
    "AU": "Australien",
    "AW": "Aruba",
    "AX": "Aland",
    "AZ": "Aserbaidschan",
    "BA": "Bosnien und Herzegowina",
    "BB": "Barbados",
    "BD": "Bangladesch",
    "BE": "Belgien",
    "BF": "Burkina Faso",
    "BG": "Bulgarien",
    "BH": "Bahrain",
    "BI": "Burundi",
    "BJ": "Benin",
    "BL": "Saint-Barthélemy",
    "BM": "Bermuda",
    "BN": "Brunei Darussalam",
    "BO": "Bolivien",
    "BQ": "Bonaire, Sint Eustatius und Saba (Niederlande)",
    "BR": "Brasilien",
    "BS": "Bahamas",
    "BT": "Bhutan",
    "BV": "Bouvetinsel",
    "BW": "Botswana",
    "BY": "Belarus (Weißrussland)",
    "BZ": "Belize",
    "CA": "Kanada",
    "CC": "Kokosinseln",
    "CD": "Kongo, Demokratische Republik (ehem. Zaire)",
    "CF": "Zentralafrikanische Republik",
    "CG": "Republik Kongo",
    "CH": "Schweiz",
    "CI": "Cote d'Ivoire",
    "CK": "Cookinseln",
    "CL": "Chile",
    "CM": "Kamerun",
    "CN": "Volksrepublik China",
    "CO": "Kolumbien",
    "CR": "Costa Rica",
    "CU": "Kuba",
    "CV": "Kap Verde",
    "CW": "Curacao",
    "CX": "Weihnachtsinsel",
    "CY": "Zypern",
    "CZ": "Tschechische Republik",
    "DD": "Deutsche Demokratische Republik (historisch)",
    "DE": "Deutschland",
    "DJ": "Dschibuti",
    "DK": "Dänemark",
    "DM": "Dominica",
    "DO": "Dominikanische Republik",
    "DZ": "Algerien",
    "EC": "Ecuador",
    "EE": "Estland",
    "EG": "Ägypten",
    "EH": "Westsahara",
    "ER": "Eritrea",
    "ES": "Spanien",
    "ET": "Athiopien",
    "FJ": "Fidschi",
    "FK": "Falklandinseln",
    "FM": "Mikronesien",
    "FO": "Färöer",
    "FR": "Frankreich",
    "GA": "Gabun",
    "GD": "Grenada",
    "GE": "Georgien",
    "GF": "Französisch-Guayana",
    "GG": "Guernsey (Kanalinsel)",
    "GH": "Ghana",
    "GI": "Gibraltar",
    "GL": "Grönland",
    "GM": "Gambia",
    "GN": "Guinea",
    "GP": "Guadeloupe",
    "GQ": "Äquatorialguinea",
    "GR": "Griechenland",
    "GS": "Südgeorgien und die Südlichen Sandwichinseln",
    "GT": "Guatemala",
    "GU": "Guam",
    "GW": "Guinea-Bissau",
    "GY": "Guyana",
    "HK": "Hongkong",
    "HM": "Heard und McDonaldinseln",
    "HN": "Honduras",
    "HR": "Kroatien",
    "HT": "Haiti",
    "HU": "Ungarn",
    "ID": "Indonesien",
    "IE": "Irland",
    "IL": "Israel",
    "IM": "Isle of Man",
    "IN": "Indien",
    "IO": "Britisches Territorium im Indischen Ozean",
    "IQ": "Irak",
    "IR": "Iran",
    "IS": "Island",
    "IT": "Italien",
    "JE": "Jersey (Kanalinsel)",
    "JM": "Jamaika",
    "JO": "Jordanien",
    "JP": "Japan",
    "KE": "Kenia",
    "KG": "Kirgisistan",
    "KH": "Kambodscha",
    "KI": "Kiribati",
    "KM": "Komoren",
    "KN": "St. Kitts und Nevis",
    "KP": "Nordkorea",
    "KR": "Südkorea",
    "KW": "Kuwait",
    "KY": "Kaimaninseln",
    "KZ": "Kasachstan",
    "LA": "Laos",
    "LB": "Libanon",
    "LC": "St. Lucia",
    "LI": "Liechtenstein",
    "LK": "Sri Lanka",
    "LR": "Liberia",
    "LS": "Lesotho",
    "LT": "Litauen",
    "LU": "Luxemburg",
    "LV": "Lettland",
    "LY": "Libyen",
    "MA": "Marokko",
    "MC": "Monaco",
    "MD": "Moldawien (Republik Moldau)",
    "ME": "Montenegro",
    "MF": "Saint-Martin (franz. Teil)",
    "MG": "Madagaskar",
    "MH": "Marshallinseln",
    "MK": "Mazedonien",
    "ML": "Mali",
    "MM": "Myanmar (Burma)",
    "MN": "Mongolei",
    "MO": "Macau",
    "MP": "Nördliche Marianen",
    "MQ": "Martinique",
    "MR": "Mauretanien",
    "MS": "Montserrat",
    "MT": "Malta",
    "MU": "Mauritius",
    "MV": "Malediven",
    "MW": "Malawi",
    "MX": "Mexiko",
    "MY": "Malaysia",
    "MZ": "Mosambik",
    "NA": "Namibia",
    "NC": "Neukaledonien",
    "NE": "Niger",
    "NF": "Norfolkinsel",
    "NG": "Nigeria",
    "NI": "Nicaragua",
    "NL": "Niederlande",
    "NO": "Norwegen",
    "NP": "Nepal",
    "NR": "Nauru",
    "NU": "Niue",
    "NZ": "Neuseeland",
    "OM": "Oman",
    "PA": "Panama",
    "PE": "Peru",
    "PF": "Französisch-Polynesien",
    "PG": "Papua-Neuguinea",
    "PH": "Philippinen",
    "PK": "Pakistan",
    "PL": "Polen",
    "PM": "St. Pierre und Miquelon",
    "PN": "Pitcairninseln",
    "PR": "Puerto Rico",
    "PS": "Palästina",
    "PT": "Portugal",
    "PW": "Palau",
    "PY": "Paraguay",
    "QA": "Katar",
    "RE": "Réunion",
    "RO": "Rumanien",
    "RS": "Serbien",
    "RU": "Russland",
    "RW": "Ruanda",
    "SA": "Saudi-Arabien",
    "SB": "Salomonen",
    "SC": "Seychellen",
    "SD": "Sudan",
    "SE": "Schweden",
    "SG": "Singapur",
    "SH": "St. Helena",
    "SI": "Slowenien",
    "SJ": "Svalbard und Jan Mayen",
    "SK": "Slowakei",
    "SL": "Sierra Leone",
    "SM": "San Marino",
    "SN": "Senegal",
    "SO": "Somalia",
    "SR": "Suriname",
    "SS": "Südsudan",
    "ST": "Sao Tomé und Príncipe",
    "SV": "El Salvador",
    "SX": "Sint Maarten (niederl. Teil)",
    "SY": "Syrien",
    "SZ": "Swasiland",
    "TC": "Turks- und Caicosinseln",
    "TD": "Tschad",
    "TF": "Französische Süd- und Antarktisgebiete",
    "TG": "Togo",
    "TH": "Thailand",
    "TJ": "Tadschikistan",
    "TK": "Tokelau",
    "TM": "Turkmenistan",
    "TN": "Tunesien",
    "TO": "Tonga",
    "TR": "Türkei",
    "TT": "Trinidad und Tobago",
    "TV": "Tuvalu",
    "TW": "Republik China (Taiwan)",
    "TZ": "Vereinigte Republik Tansania",
    "UA": "Ukraine",
    "UG": "Uganda",
    "UM": "United States Minor Outlying Islands",
    "US": "Vereinigte Staaten von Amerika",
    "UY": "Uruguay",
    "UZ": "Usbekistan",
    "VA": "Vatikanstadt",
    "VC": "St. Vincent und die Grenadinen",
    "VE": "Venezuela",
    "VG": "Britische Jungferninseln",
    "VI": "Amerikanische Jungferninseln",
    "VN": "Vietnam",
    "VU": "Vanuatu",
    "WF": "Wallis und Futuna",
    "WS": "Samoa",
    "YE": "Jemen",
    "YT": "Mayotte",
    "ZA": "Südafrika",
    "ZM": "Sambia",
    "ZW": "Simbabwe"
}

This helped a lot, but here is a corrected version by a native speaker:

var isoCountries = {
"AD": "Andorra",
"AE": "Vereinigte Arabische Emirate",
"AF": "Afghanistan",
"AG": "Antigua und Barbuda",
"AI": "Anguilla",
"AL": "Albanien",
"AM": "Armenien",
"AN": "Niederländische Antillen (ehemalig)",
"AO": "Angola",
"AQ": "Antarktika",
"AR": "Argentinien",
"AS": "Amerikanisch-Samoa",
"AT": "Österreich",
"AU": "Australien",
"AW": "Aruba",
"AX": "Aland",
"AZ": "Aserbaidschan",
"BA": "Bosnien und Herzegowina",
"BB": "Barbados",
"BD": "Bangladesch",
"BE": "Belgien",
"BF": "Burkina Faso",
"BG": "Bulgarien",
"BH": "Bahrain",
"BI": "Burundi",
"BJ": "Benin",
"BL": "Saint-Barthélemy",
"BM": "Bermuda",
"BN": "Brunei Darussalam",
"BO": "Bolivien",
"BQ": "Bonaire, Sint Eustatius und Saba (Niederlande)",
"BR": "Brasilien",
"BS": "Bahamas",
"BT": "Bhutan",
"BV": "Bouvetinsel",
"BW": "Botswana",
"BY": "Belarus (Weißrussland)",
"BZ": "Belize",
"CA": "Kanada",
"CC": "Kokosinseln",
"CD": "Kongo, Demokratische Republik (ehem. Zaire)",
"CF": "Zentralafrikanische Republik",
"CG": "Republik Kongo",
"CH": "Schweiz",
"CI": "Cote d'Ivoire",
"CK": "Cookinseln",
"CL": "Chile",
"CM": "Kamerun",
"CN": "Volksrepublik China",
"CO": "Kolumbien",
"CR": "Costa Rica",
"CU": "Kuba",
"CV": "Kap Verde",
"CW": "Curacao",
"CX": "Weihnachtsinsel",
"CY": "Zypern",
"CZ": "Tschechische Republik",
"DD": "Deutsche Demokratische Republik (historisch)",
"DE": "Deutschland",
"DJ": "Dschibuti",
"DK": "Dänemark",
"DM": "Dominica",
"DO": "Dominikanische Republik",
"DZ": "Algerien",
"EC": "Ecuador",
"EE": "Estland",
"EG": "Ägypten",
"EH": "Westsahara",
"ER": "Eritrea",
"ES": "Spanien",
"ET": "Athiopien",
"FJ": "Fidschi",
"FK": "Falklandinseln",
"FM": "Mikronesien",
"FO": "Färöer",
"FR": "Frankreich",
"GA": "Gabun",
"GD": "Grenada",
"GE": "Georgien",
"GF": "Französisch-Guayana",
"GG": "Guernsey (Kanalinsel)",
"GH": "Ghana",
"GI": "Gibraltar",
"GL": "Grönland",
"GM": "Gambia",
"GN": "Guinea",
"GP": "Guadeloupe",
"GQ": "Äquatorialguinea",
"GR": "Griechenland",
"GS": "Südgeorgien und die Südlichen Sandwichinseln",
"GT": "Guatemala",
"GU": "Guam",
"GW": "Guinea-Bissau",
"GY": "Guyana",
"HK": "Hongkong",
"HM": "Heard und McDonaldinseln",
"HN": "Honduras",
"HR": "Kroatien",
"HT": "Haiti",
"HU": "Ungarn",
"ID": "Indonesien",
"IE": "Irland",
"IL": "Israel",
"IM": "Isle of Man",
"IN": "Indien",
"IO": "Britisches Territorium im Indischen Ozean",
"IQ": "Irak",
"IR": "Iran",
"IS": "Island",
"IT": "Italien",
"JE": "Jersey (Kanalinsel)",
"JM": "Jamaika",
"JO": "Jordanien",
"JP": "Japan",
"KE": "Kenia",
"KG": "Kirgisistan",
"KH": "Kambodscha",
"KI": "Kiribati",
"KM": "Komoren",
"KN": "St. Kitts und Nevis",
"KP": "Nordkorea",
"KR": "Südkorea",
"KW": "Kuwait",
"KY": "Kaimaninseln",
"KZ": "Kasachstan",
"LA": "Laos",
"LB": "Libanon",
"LC": "St. Lucia",
"LI": "Liechtenstein",
"LK": "Sri Lanka",
"LR": "Liberia",
"LS": "Lesotho",
"LT": "Litauen",
"LU": "Luxemburg",
"LV": "Lettland",
"LY": "Libyen",
"MA": "Marokko",
"MC": "Monaco",
"MD": "Moldawien (Republik Moldau)",
"ME": "Montenegro",
"MF": "Saint-Martin (franz. Teil)",
"MG": "Madagaskar",
"MH": "Marshallinseln",
"MK": "Mazedonien",
"ML": "Mali",
"MM": "Myanmar (Burma)",
"MN": "Mongolei",
"MO": "Macau",
"MP": "Nördliche Marianen",
"MQ": "Martinique",
"MR": "Mauretanien",
"MS": "Montserrat",
"MT": "Malta",
"MU": "Mauritius",
"MV": "Malediven",
"MW": "Malawi",
"MX": "Mexiko",
"MY": "Malaysia",
"MZ": "Mosambik",
"NA": "Namibia",
"NC": "Neukaledonien",
"NE": "Niger",
"NF": "Norfolkinsel",
"NG": "Nigeria",
"NI": "Nicaragua",
"NL": "Niederlande",
"NO": "Norwegen",
"NP": "Nepal",
"NR": "Nauru",
"NU": "Niue",
"NZ": "Neuseeland",
"OM": "Oman",
"PA": "Panama",
"PE": "Peru",
"PF": "Französisch-Polynesien",
"PG": "Papua-Neuguinea",
"PH": "Philippinen",
"PK": "Pakistan",
"PL": "Polen",
"PM": "St. Pierre und Miquelon",
"PN": "Pitcairninseln",
"PR": "Puerto Rico",
"PS": "Palästina",
"PT": "Portugal",
"PW": "Palau",
"PY": "Paraguay",
"QA": "Katar",
"RE": "Réunion",
"RO": "Rumanien",
"RS": "Serbien",
"RU": "Russland",
"RW": "Ruanda",
"SA": "Saudi-Arabien",
"SB": "Salomonen",
"SC": "Seychellen",
"SD": "Sudan",
"SE": "Schweden",
"SG": "Singapur",
"SH": "St. Helena",
"SI": "Slowenien",
"SJ": "Svalbard und Jan Mayen",
"SK": "Slowakei",
"SL": "Sierra Leone",
"SM": "San Marino",
"SN": "Senegal",
"SO": "Somalia",
"SR": "Suriname",
"SS": "Südsudan",
"ST": "Sao Tomé und Príncipe",
"SV": "El Salvador",
"SX": "Sint Maarten (niederl. Teil)",
"SY": "Syrien",
"SZ": "Swasiland",
"TC": "Turks- und Caicosinseln",
"TD": "Tschad",
"TF": "Französische Süd- und Antarktisgebiete",
"TG": "Togo",
"TH": "Thailand",
"TJ": "Tadschikistan",
"TK": "Tokelau",
"TM": "Turkmenistan",
"TN": "Tunesien",
"TO": "Tonga",
"TR": "Türkei",
"TT": "Trinidad und Tobago",
"TV": "Tuvalu",
"TW": "Republik China (Taiwan)",
"TZ": "Vereinigte Republik Tansania",
"UA": "Ukraine",
"UG": "Uganda",
"UM": "United States Minor Outlying Islands",
"US": "Vereinigte Staaten von Amerika",
"UY": "Uruguay",
"UZ": "Usbekistan",
"VA": "Vatikanstadt",
"VC": "St. Vincent und die Grenadinen",
"VE": "Venezuela",
"VG": "Britische Jungferninseln",
"VI": "Amerikanische Jungferninseln",
"VN": "Vietnam",
"VU": "Vanuatu",
"WF": "Wallis und Futuna",
"WS": "Samoa",
"YE": "Jemen",
"YT": "Mayotte",
"ZA": "Südafrika",
"ZM": "Sambia",
"ZW": "Simbabwe"
};

commited! @luwe1204 thanks for your update!