JSFiddle - React, Tailwind, and code Playground

HTML

<form id="myForm">
    <input list="answers" id="answer">
    <datalist id="answers">
        <option data-value="42">The answer</option>
        <option data-value="1337">Elite</option>
        <option data-value="69">Dirty</option>
        <option data-value="3">Pi</option>
    </datalist>
    <input type="hidden" name="answer" id="answer-hidden">
    <input type="submit">
</form>

<p>Submitted value (for debugging):</p>
<pre id="result"></pre>

JavaScript

document.querySelector('input[list]').addEventListener('input', function(e) {
    var input = e.target,
        list = input.getAttribute('list'),
        options = document.querySelectorAll('#' + list + ' option'),
        hiddenInput = document.getElementById(input.getAttribute('id') + '-hidden'),
        label = input.value;

    hiddenInput.value = label;

    for(var i = 0; i < options.length; i++) {
        var option = options[i];

        if(option.innerText === label) {
            hiddenInput.value = option.getAttribute('data-value');
            break;
        }
    }
});

// For debugging purposes
document.getElementById("myForm").addEventListener('submit', function(e) {
    var value = document.getElementById('answer-hidden').value;
    document.getElementById('result').innerHTML = value;
    e.preventDefault();
});