JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app>
<div ng-controller="testCtrl">
    <select multiple="multiple" ng-model="first" ng-options="c.name for c in listObj">
    </select>
    <select multiple="multiple" ng-model="second" ng-options="item for item in first[0].content">
    </select>
    <hr/>
    {{first}}
</div>
</div>

JavaScript

function testCtrl($scope) {
    $scope.listObj = [{name: "x", content: [1,2,3]},
                      {name: "y", content: [4,5,6]}];
    
}