Nintex Forms multiselect field not saving data added with JavaScript

[warrenbarton]

Hello! I have a classic form with a multiselect field. In some cases, i need to select an option with JavaScript.

The option in the second box is the selected option added with JavaScript. But if i save the form, it doesnt saves this data, the second box will be empty. If i add another option with the add button, all data will be saved, the one added with JavaScript too.

This is the JS:

Thank you very much!