Selectize.js manually add some items

Try this.

 $('.select-ajax-city').each(function() {
    if (this.selectize) {
        for(x=0; x < 10; ++x){
            this.selectize.addOption({value:x, text: x});
        }
    }
});  

This plugin does not attempt to load an item metadata from the server. You need to first add an option using addOption() method. Next, you can use addItem().

v.selectize.addOption({value:13,text:'foo'}); //option can be created manually or loaded using Ajax
v.selectize.addItem(13); 

You can add options like this:

var $select = $(document.getElementById('mySelect')).selectize(options);
var selectize = $select[0].selectize;
selectize.addOption({value: 1, text: 'whatever'});
selectize.refreshOptions();

This only adds the option as possible selection. Now you can use addItem to add the new option to the list:

selectize.addItem(1);

This does not need a refresh function. You do not need to use "refreshOptions" if you add the new option immediately.