Using input with datalist as select - how do I open a full list of values if a value is already selected?

input.onmousedown = event => {
  // if value is not empty
  if (input.value) {
    // cancel event procedure
    event.preventDefault();
    // hold current placeholder
    input._placeholder = input.placeholder;
    // set placeholder to the value
    input.placeholder = input.value;
    // clear current value
    input.value = '';
    // add flip-flag class
    input.classList.add('flip-value-placeholder');
    // refocus
    input.blur();
    input.focus();
  }
};

input.onkeydown = () => {
  // if input has flip-flag class
  if (input.classList.contains('flip-value-placeholder')) {
    // remove class
    input.classList.remove('flip-value-placeholder');
    // rollback the value
    input.value = input.placeholder;
    // rollback placeholder
    input.placeholder = input._placeholder;
  }
}

form.onsubmit = event => {
  // find all inputs with list by selector
  form.querySelectorAll('input[list]')
    // just to be sure, do a flip reset
    .forEach(input=>input.onkeydown());
  // get form data
  const data = new FormData(form);
  // alert data
  alert(JSON.stringify([...data.entries()]));
  // cancel event procedure 
  event.preventDefault();
  event.stopPropagation();
}

/* recolor placeholder */
input.flip-value-placeholder::placeholder {
  color: currentcolor;
}


/* remove the caret */
input.flip-value-placeholder {
  caret-color: transparent;
}

<form id="form">
  <input name="country" placeholder="Country" id="input" list="datalist" />
  <datalist id="datalist">
    <option>&nbsp;</option>
    <option>Afghanistan</option>
    <option>Albania</option>
    <option>Algeria</option>
    <option>Andorra</option>
    <option>Angola</option>
    <option>Antigua and Barbuda</option>
    <option>Argentina</option>
    <option>Armenia</option>
    <option>Australia</option>
    <option>Austria</option>
    <option>Azerbaijan</option>
    <option>Bahamas</option>
    <option>Bahrain</option>
    <option>Bangladesh</option>
    <option>Barbados</option>
    <option>Belarus</option>
    <option>Belgium</option>
    <option>Belize</option>
    <option>Benin</option>
    <option>Bhutan</option>
    <option>Bolivia</option>
    <option>Bosnia and Herzegovina</option>
    <option>Botswana</option>
    <option>Brazil</option>
    <option>Brunei </option>
    <option>Bulgaria</option>
    <option>Burkina Faso</option>
    <option>Burundi</option>
    <option>Côte d'Ivoire</option>
    <option>Cabo Verde</option>
    <option>Cambodia</option>
    <option>Cameroon</option>
    <option>Canada</option>
    <option>Central African Republic</option>
    <option>Chad</option>
    <option>Chile</option>
    <option>China</option>
    <option>Colombia</option>
    <option>Comoros</option>
    <option>Congo (Congo-Brazzaville)</option>
    <option>Costa Rica</option>
    <option>Croatia</option>
    <option>Cuba</option>
    <option>Cyprus</option>
    <option>Czechia (Czech Republic)</option>
    <option>Democratic Republic of the Congo</option>
    <option>Denmark</option>
    <option>Djibouti</option>
    <option>Dominica</option>
    <option>Dominican Republic</option>
    <option>Ecuador</option>
    <option>Egypt</option>
    <option>El Salvador</option>
    <option>Equatorial Guinea</option>
    <option>Eritrea</option>
    <option>Estonia</option>
    <option>Eswatini (fmr. "Swaziland")</option>
    <option>Ethiopia</option>
    <option>Fiji</option>
    <option>Finland</option>
    <option>France</option>
    <option>Gabon</option>
    <option>Gambia</option>
    <option>Georgia</option>
    <option>Germany</option>
    <option>Ghana</option>
    <option>Greece</option>
    <option>Grenada</option>
    <option>Guatemala</option>
    <option>Guinea</option>
    <option>Guinea-Bissau</option>
    <option>Guyana</option>
    <option>Haiti</option>
    <option>Holy See</option>
    <option>Honduras</option>
    <option>Hungary</option>
    <option>Iceland</option>
    <option>India</option>
    <option>Indonesia</option>
    <option>Iran</option>
    <option>Iraq</option>
    <option>Ireland</option>
    <option>Israel</option>
    <option>Italy</option>
    <option>Jamaica</option>
    <option>Japan</option>
    <option>Jordan</option>
    <option>Kazakhstan</option>
    <option>Kenya</option>
    <option>Kiribati</option>
    <option>Kuwait</option>
    <option>Kyrgyzstan</option>
    <option>Laos</option>
    <option>Latvia</option>
    <option>Lebanon</option>
    <option>Lesotho</option>
    <option>Liberia</option>
    <option>Libya</option>
    <option>Liechtenstein</option>
    <option>Lithuania</option>
    <option>Luxembourg</option>
    <option>Madagascar</option>
    <option>Malawi</option>
    <option>Malaysia</option>
    <option>Maldives</option>
    <option>Mali</option>
    <option>Malta</option>
    <option>Marshall Islands</option>
    <option>Mauritania</option>
    <option>Mauritius</option>
    <option>Mexico</option>
    <option>Micronesia</option>
    <option>Moldova</option>
    <option>Monaco</option>
    <option>Mongolia</option>
    <option>Montenegro</option>
    <option>Morocco</option>
    <option>Mozambique</option>
    <option>Myanmar (formerly Burma)</option>
    <option>Namibia</option>
    <option>Nauru</option>
    <option>Nepal</option>
    <option>Netherlands</option>
    <option>New Zealand</option>
    <option>Nicaragua</option>
    <option>Niger</option>
    <option>Nigeria</option>
    <option>North Korea</option>
    <option>North Macedonia</option>
    <option>Norway</option>
    <option>Oman</option>
    <option>Pakistan</option>
    <option>Palau</option>
    <option>Palestine State</option>
    <option>Panama</option>
    <option>Papua New Guinea</option>
    <option>Paraguay</option>
    <option>Peru</option>
    <option>Philippines</option>
    <option>Poland</option>
    <option>Portugal</option>
    <option>Qatar</option>
    <option>Romania</option>
    <option>Russia</option>
    <option>Rwanda</option>
    <option>Saint Kitts and Nevis</option>
    <option>Saint Lucia</option>
    <option>Saint Vincent and the Grenadines</option>
    <option>Samoa</option>
    <option>San Marino</option>
    <option>Sao Tome and Principe</option>
    <option>Saudi Arabia</option>
    <option>Senegal</option>
    <option>Serbia</option>
    <option>Seychelles</option>
    <option>Sierra Leone</option>
    <option>Singapore</option>
    <option>Slovakia</option>
    <option>Slovenia</option>
    <option>Solomon Islands</option>
    <option>Somalia</option>
    <option>South Africa</option>
    <option>South Korea</option>
    <option>South Sudan</option>
    <option>Spain</option>
    <option>Sri Lanka</option>
    <option>Sudan</option>
    <option>Suriname</option>
    <option>Sweden</option>
    <option>Switzerland</option>
    <option>Syria</option>
    <option>Tajikistan</option>
    <option>Tanzania</option>
    <option>Thailand</option>
    <option>Timor-Leste</option>
    <option>Togo</option>
    <option>Tonga</option>
    <option>Trinidad and Tobago</option>
    <option>Tunisia</option>
    <option>Turkey</option>
    <option>Turkmenistan</option>
    <option>Tuvalu</option>
    <option>Uganda</option>
    <option>Ukraine</option>
    <option>United Arab Emirates</option>
    <option>United Kingdom</option>
    <option>United States of America</option>
    <option>Uruguay</option>
    <option>Uzbekistan</option>
    <option>Vanuatu</option>
    <option>Venezuela</option>
    <option>Vietnam</option>
    <option>Yemen</option>
    <option>Zambia</option>
    <option>Zimbabwe</option>
  </datalist>
  <button id="button" type="submit">Submit</button>
</form>