Trying to convert a string inside a search form to lowercase

Question

I am trying to search for a "Country name" in uppercase and lowercase. It currently only works for uppercase for example: "USA" "Cambodia" . Is toLowerCase() an option? I tried but it's not working. I might be using it incorrectly. Thank you!

My code:

const filterCountries = results.filter((item) => {
    return searchCountries !== ""
      ? item.country.includes(searchCountries)
      : item;
});

Answer 1

If you are trying to do a case-insensitive search/filtering then you should ignore the casing of both terms, or in other words, make the casing the same between them. Filtering an array means the filter callback should return true/false for the current element being filtered. If the search term is falsey then return true to allow the element through.

const filterCountries = results.filter(({ country }) => {
  const searchTerm = searchCountries.toLowerCase();
  return searchTerm
    ? country.toLowerCase().includes(searchTerm)
    : true;
});

Fun fact, all strings include the sub-string "", so checking if the search term is truthy/falsey is rather irrelevant. You can simply check if it is included in the country string.

const filterCountries = results.filter(({ country }) => {
  const searchTerm = searchCountries.toLowerCase();
  return country.toLowerCase().includes(searchTerm);
});

Answer 2

If you are trying to search the countries based on the searchTerm then you can try the following:

const filterCountries = results.filter((item) => {
    return item.country.toLowerCase().includes(searchCountries.toLowerCase())
     
});

Sample Example:

const countryList = [
"Afghanistan",
"Albania",
"Algeria",
"American Samoa",
"Andorra",
"Angola",
"Anguilla",
"Antarctica",
"Antigua and Barbuda",
"Argentina",
"Armenia",
"Aruba",
"Australia",
"Austria",
"Azerbaijan",
"Bahamas (the)",
"Bahrain",
"Bangladesh",
"Barbados",
"Belarus",
"Belgium",
"Belize",
"Benin",
"Bermuda",
"Bhutan",
"Bolivia (Plurinational State of)",
"Bonaire, Sint Eustatius and Saba",
"Bosnia and Herzegovina",
"Botswana",
"Bouvet Island",
"Brazil",
"British Indian Ocean Territory (the)",
"Brunei Darussalam",
"Bulgaria",
"Burkina Faso",
"Burundi",
"Cabo Verde",
"Cambodia",
"Cameroon",
"Canada",
"Cayman Islands (the)",
"Central African Republic (the)",
"Chad",
"Chile",
"China",
"Christmas Island",
"Cocos (Keeling) Islands (the)",
"Colombia",
"Comoros (the)",
"Congo (the Democratic Republic of the)",
"Congo (the)",
"Cook Islands (the)",
"Costa Rica",
"Croatia",
"Cuba",
"Curaçao",
"Cyprus",
"Czechia",
"Côte d'Ivoire",
"Denmark",
"Djibouti",
"Dominica",
"Dominican Republic (the)",
"Ecuador",
"Egypt",
"El Salvador",
"Equatorial Guinea",
"Eritrea",
"Estonia",
"Eswatini",
"Ethiopia",
"Falkland Islands (the) [Malvinas]",
"Faroe Islands (the)",
"Fiji",
"Finland",
"France",
"French Guiana",
"French Polynesia",
"French Southern Territories (the)",
"Gabon",
"Gambia (the)",
"Georgia",
"Germany",
"Ghana",
"Gibraltar",
"Greece",
"Greenland",
"Grenada",
"Guadeloupe",
"Guam",
"Guatemala",
"Guernsey",
"Guinea",
"Guinea-Bissau",
"Guyana",
"Haiti",
"Heard Island and McDonald Islands",
"Holy See (the)",
"Honduras",
"Hong Kong",
"Hungary",
"Iceland",
"India",
"Indonesia",
"Iran (Islamic Republic of)",
"Iraq",
"Ireland",
"Isle of Man",
"Israel",
"Italy",
"Jamaica",
"Japan",
"Jersey",
"Jordan",
"Kazakhstan",
"Kenya",
"Kiribati",
"Korea (the Democratic People's Republic of)",
"Korea (the Republic of)",
"Kuwait",
"Kyrgyzstan",
"Lao People's Democratic Republic (the)",
"Latvia",
"Lebanon",
"Lesotho",
"Liberia",
"Libya",
"Liechtenstein",
"Lithuania",
"Luxembourg",
"Macao",
"Madagascar",
"Malawi",
"Malaysia",
"Maldives",
"Mali",
"Malta",
"Marshall Islands (the)",
"Martinique",
"Mauritania",
"Mauritius",
"Mayotte",
"Mexico",
"Micronesia (Federated States of)",
"Moldova (the Republic of)",
"Monaco",
"Mongolia",
"Montenegro",
"Montserrat",
"Morocco",
"Mozambique",
"Myanmar",
"Namibia",
"Nauru",
"Nepal",
"Netherlands (the)",
"New Caledonia",
"New Zealand",
"Nicaragua",
"Niger (the)",
"Nigeria",
"Niue",
"Norfolk Island",
"Northern Mariana Islands (the)",
"Norway",
"Oman",
"Pakistan",
"Palau",
"Palestine, State of",
"Panama",
"Papua New Guinea",
"Paraguay",
"Peru",
"Philippines (the)",
"Pitcairn",
"Poland",
"Portugal",
"Puerto Rico",
"Qatar",
"Republic of North Macedonia",
"Romania",
"Russian Federation (the)",
"Rwanda",
"Réunion",
"Saint Barthélemy",
"Saint Helena, Ascension and Tristan da Cunha",
"Saint Kitts and Nevis",
"Saint Lucia",
"Saint Martin (French part)",
"Saint Pierre and Miquelon",
"Saint Vincent and the Grenadines",
"Samoa",
"San Marino",
"Sao Tome and Principe",
"Saudi Arabia",
"Senegal",
"Serbia",
"Seychelles",
"Sierra Leone",
"Singapore",
"Sint Maarten (Dutch part)",
"Slovakia",
"Slovenia",
"Solomon Islands",
"Somalia",
"South Africa",
"South Georgia and the South Sandwich Islands",
"South Sudan",
"Spain",
"Sri Lanka",
"Sudan (the)",
"Suriname",
"Svalbard and Jan Mayen",
"Sweden",
"Switzerland",
"Syrian Arab Republic",
"Taiwan",
"Tajikistan",
"Tanzania, United Republic of",
"Thailand",
"Timor-Leste",
"Togo",
"Tokelau",
"Tonga",
"Trinidad and Tobago",
"Tunisia",
"Turkey",
"Turkmenistan",
"Turks and Caicos Islands (the)",
"Tuvalu",
"Uganda",
"Ukraine",
"United Arab Emirates (the)",
"United Kingdom of Great Britain and Northern Ireland (the)",
"United States Minor Outlying Islands (the)",
"United States of America (the)",
"Uruguay",
"Uzbekistan",
"Vanuatu",
"Venezuela (Bolivarian Republic of)",
"Viet Nam",
"Virgin Islands (British)",
"Virgin Islands (U.S.)",
"Wallis and Futuna",
"Western Sahara",
"Yemen",
"Zambia",
"Zimbabwe",
"Åland Islands"
];
let searchCountries = "India";

const filterCountries = countryList.filter((item) => {
return item.toLowerCase().includes(searchCountries.toLowerCase())
});

console.log(filterCountries)