Repetitive data when loading a select - arrays

Question

I'm calling EventListener so that when something is typed into the username field, it will list that user's companies for me.
var ent = document.getElementById("username");
//var str = "";
ent.addEventListener('change', async () => {
localStorage.clear();
self.empUsuario = new Array();
self.rucEmp = new Array();
var newUser = document.getElementById("username");
$('#empresa').empty();
await fetch(environment.apiPoint + '/empresas?usuario=' + newUser.value, {
method: 'GET',
headers: {
'Content-Type': 'application/json'
}
})
.then(res => res.json())
.then(datos => {
datos.forEach(e => {
self.todasEmpresasUsuario.push({
ruc: e.ruc,
nombEmp: e.nombreCorto
});
});
})
await self.todasEmpresasUsuario().forEach(
function (element) {
self.empUsuario.push(element.nombEmp);
self.rucEmp.push(element.ruc);
}
);
Then I give it a conditional if the user is different from null, that it shows me with the rucEmp, and if not an empty space.
var str = "";
var item = "";
if (newUser.value != '') {
self.cont = 0;
let vacio = '';
for (item of self.empUsuario) {
vacio = "<option value=''>" + ' ' + "</option>"
str += "<option value='" + self.rucEmp[self.cont] + "'>" + item + "</option>"
self.cont++;
}
if (newUser.value == '') {
//str += "";
str += "<option value='" + self.rucEmp[self.cont] + "'>" + item + "</option>"
$('#empresa').empty().append(str);
}
$('#empresa').empty().append(vacio + str);
}
I expected the company lists to appear for each user and not accumulate, but the lists accumulate in the select.
enter image description here