JSFiddle - React, Tailwind, and code Playground

HTML

<form action="" method="post" name="formu">
    <div class="gauche largeur640px" style="padding: 0 0 5px 0;">
        <div class="gauche" style="width: 150px; padding: 10px 0 0 5px;">Lundi</div>
        <div id="HD_1" class="gauche centrer" style="width: 340px;">
            <div class="gauche centrer tranche_hor_1" id="tranche_1_0" style="width: 340px; margin-top: 7px;">De
                <input type="text" name="from_d_1[]" class="margeHautMoins4px timeClass ui-timepicker-input" style="width: 60px;" value="8:00" autocomplete="off" />à
                <input type="text" name="from_f_1[]" class="margeHautMoins4px timeClass ui-timepicker-input" style="width: 60px;" value="12:00" autocomplete="off" />
            </div>
            <div class="gauche centrer tranche_hor_1" id="tranche_1_1" style="width: 340px; margin-top: 7px;">De
                <input type="text" name="from_d_1[]" class="margeHautMoins4px timeClass ui-timepicker-input" style="width: 60px;" value="14:00" autocomplete="off" />à
                <input type="text" name="from_f_1[]" class="margeHautMoins4px timeClass ui-timepicker-input" style="width: 60px;" value="18:00" autocomplete="off" />
            </div>
        </div>
    </div>
    <input id="foo" class="lienBoutonRouge" type="button" name="valider_form" value="Continuer" />
</form>

JavaScript

$('#foo').on('click', function () {
    ValiderFormu($(this))
})

function ValiderFormu(input) {
    formulaire = jQuery(input).parents('form');
    alert(jQuery(formulaire).find('[name="from_d_1[]"]:eq(0)').val());
    alert(jQuery(formulaire).find('[name="from_d_1[]"]:eq(1)').val());
}