Bold substring in React export const getJsxWithBoldSubstr = (text, subString) => { const regExp = new RegExp(`(${subString})`, 'gi') return text.split(regExp).map((str, index) => regExp.test(str) ? <b key={`char-${index}`}>{str}</b> : str) } Example with items filtering const countriesAll = ['Afghanistan', 'Albania', 'Algeria', 'Andorra', 'Angola', 'Anguilla', 'Antigua Barbuda', 'Argentina', 'Armenia', 'Aruba', 'Australia', 'Austria', 'Azerbaijan', 'Bahamas', 'Bahrain', 'Bangladesh', 'Barbados', 'Belarus', 'Belgium', 'Belize', 'Benin', 'Bermuda', 'Bhutan', 'Bolivia', 'Bosnia Herzegovina', 'Botswana', 'Brazil', 'British Virgin Islands', 'Brunei', 'Bulgaria', 'Burkina Faso', 'Burundi', 'Cambodia', 'Cameroon', 'Cape Verde', 'Cayman Islands', 'Chad', 'Chile', 'China', 'Colombia', 'Congo', 'Cook Islands', 'Costa Rica', 'Cote D Ivoire', 'Croatia', 'Cruise Ship', 'Cuba', 'Cyprus', 'Czech Republic', 'Denmark', 'Djibouti', 'Dominica', 'Dominican Republic', 'Ecuador', 'Egypt', 'El Salvador', 'Equatorial Guinea', 'Estonia', 'Ethiopia', 'Falkland Islands', 'Faroe Islands', 'Fiji', 'Finland', 'France', 'French Polynesia', 'French West Indies', 'Gabon', 'Gambia', 'Georgia', 'Germany', 'Ghana', 'Gibraltar', 'Greece', 'Greenland', 'Grenada', 'Guam', 'Guatemala', 'Guernsey', 'Guinea', 'Guinea Bissau', 'Guyana', 'Haiti', 'Honduras', 'Hong Kong', 'Hungary', 'Iceland', 'India', 'Indonesia', 'Iran', 'Iraq', 'Ireland', 'Isle of Man', 'Israel', 'Italy', 'Jamaica', 'Japan', 'Jersey', 'Jordan', 'Kazakhstan', 'Kenya', 'Kuwait', 'Kyrgyz Republic', 'Laos', 'Latvia', 'Lebanon', 'Lesotho', 'Liberia', 'Libya', 'Liechtenstein', 'Lithuania', 'Luxembourg', 'Macau', 'Macedonia', 'Madagascar', 'Malawi', 'Malaysia', 'Maldives', 'Mali', 'Malta', 'Mauritania', 'Mauritius', 'Mexico', 'Moldova', 'Monaco', 'Mongolia', 'Montenegro', 'Montserrat', 'Morocco', 'Mozambique', 'Namibia', 'Nepal', 'Netherlands', 'Netherlands Antilles', 'New Caledonia', 'New Zealand', 'Nicaragua', 'Niger', 'Nigeria', 'Norway', 'Oman', 'Pakistan', 'Palestine', 'Panama', 'Papua New Guinea', 'Paraguay', 'Peru', 'Philippines', 'Poland', 'Portugal', 'Puerto Rico', 'Qatar', 'Reunion', 'Romania', 'Russia', 'Rwanda', 'Saint Pierre Miquelon', 'Samoa', 'San Marino', 'Satellite', 'Saudi Arabia', 'Senegal', 'Serbia', 'Seychelles', 'Sierra Leone', 'Singapore', 'Slovakia', 'Slovenia', 'South Africa', 'South Korea', 'Spain', 'Sri Lanka', 'St Kitts Nevis', 'St Lucia', 'St Vincent', 'St. Lucia', 'Sudan', 'Suriname', 'Swaziland', 'Sweden', 'Switzerland', 'Syria', 'Taiwan', 'Tajikistan', 'Tanzania', 'Thailand', "Timor L'Este", 'Togo', 'Tonga', 'Trinidad Tobago', 'Tunisia', 'Turkey', 'Turkmenistan', 'Turks Caicos', 'Uganda', 'Ukraine', 'United Arab Emirates', 'United Kingdom', 'Uruguay', 'Uzbekistan', 'Venezuela', 'Vietnam', 'Virgin Islands (US)', 'Yemen', 'Zambia', 'Zimbabwe'] function Component() { const [inputValue, setInputValue] = useState('') const [countries, setCountries] = useState(countriesAll) useEffect(() => { const foundCountries = countriesAll.filter(country => country.toLowerCase().includes(inputValue.toLocaleLowerCase().trim())) setCountries(foundCountries) }, [inputValue]) return ( <> <div><input type="text" placeholder='country' value={inputValue} onChange={(e) => setInputValue(e.target.value)} /></div> <h1>Countries</h1> <ul> { countries.map(country => ( <li key={country}> { inputValue ? <span>{getJsxWithBoldSubstr(country, inputValue)}</span> : country } </li> )) } </ul> </> ) }