JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<ul data-bind="foreach: numbers">
  <li>
    <span data-bind="text: $data"></span>
    <button data-bind="click: $parent.moveUp">Move Up</button>
    <button data-bind="click: $parent.moveDown">Move down</button>
  </li>
</ul>

TypeScript

function ViewModel() {
  var _this = this;
  _this.numbers = ko.observableArray(["a", "b", "c", "d", "e"]);

  _this.moveDown = function(number) {
  	var idx = _this.numbers().indexOf(number);
    if (idx >= _this.numbers().length) return;
    _this.numbers.remove(number);
    _this.numbers.splice(idx+1, 0, number)

  }
  _this.moveUp = function(number) {
  	var idx = _this.numbers().indexOf(number);
    if (idx === 0) return;
    _this.numbers.remove(number);
    _this.numbers.splice(idx-1, 0, number)
  }
}

var vm = new ViewModel();
ko.applyBindings(vm);