I have this piece of JS:
for(var index in response.rates) {
select.options[select.options.length] = new Option([index], index);
}
It generates the and tags populated with an array.
How can I give attributes to from there? Like onselect and and other things.
Assign the option to a variable then you can give it attributes.
for(var index in response.rates) {
let option = new Option(index, index);
option.addEventListener("select", ...);
select.options[select.options.length] = option;
}