JSFiddle - React, Tailwind, and code Playground

JavaScript

$("body").append(diasHorario(2)); // seleciona Terça

function diasHorario(index) {
    var dias = Array('Segunda', 'Terça', 'Quarta', 'Quinta', 'Sexta', 'Sábado', 'Domingo');
    return dias.reduce(function (str, dia, i) {
        return str + ['<option value="', i + 1, '" ', i == index - 1 ? 'selected="selected"' : '', '>', dia, '</option>'].join('')
    }, "<select id='diasHorario' class='form-control'>") + "</select>";
}