Handle <select multiple>

[GrosSacASac]

.value works fine for single value select. But only shows the first one for select multiple

Use selectedOptions property.

[GrosSacASac]

To read current value, where select is the html node

Array.from(select.selectedOptions).map(option => {
    return option.value;
);

[GrosSacASac]

To write, cannot use selectedOptions directly. Instead go through select.options and set or remove "selected" attribute

[GrosSacASac]

One problem is that now arrays are used already for data-list