Q:

HTML Multiple select change 'None selected' text

I have a select list with multi select option:
<select data-bind="attr:{'id':'multilistS'+Id()},foreach: Hlist" multiple="multiple">
     <option data-bind="click:$root.changeShole,value:$data.Id, text:N,attr:{'selected':$data.Sel}">Cheese</option>
</select>

but I want to change the 'None Selected' text. It is possible to do this in HTML code or just in JavaScript using nonSelectedText option?

A:

You really should take John Pavek's advice to read up on the options bindings. Knockout provides good tools specifically for this, and your construction uses none of them.
noneselectedtext appears to be a feature of the jQuery-UI multiselect widget. If you are using that, then you will want to use a binding handler for it.
Here is a simple example of what you describe, with a message that changes based on whether anything in the multiselect is selected. 

const vm = {
  optionsCaption: ko.pureComputed(function() {
    return (vm.selectedOptions().length === 0) ? 'Please select at least one' : 'ok';
  }),
  selectedOptions: ko.observableArray([]),
  Hlist: ko.observableArray([{
    Id: 1,
    N: 'One'
  }, {
    Id: 2,
    N: 'Two'
  }])
};

ko.applyBindings(vm);
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<div data-bind="text: optionsCaption"></div>
<select data-bind="options: Hlist, optionsText: 'N', optionsValue: 'Id', selectedOptions: selectedOptions" multiple="multiple">
</select>
<div data-bind="foreach: selectedOptions">
  <div data-bind="text:$data"></div>
</div>

