angularjs highlight the first item in select

After the initial call to get the list of items (see below), I need get select the first item and get more details from my database. So after the items load into my select input I need to :

Highlight the first item in listbox
Pass that first itemID to DB to fetch the details of that item.

How can I do all of this within my initial page load?

<!DOCTYPE html>
<html>
<head>
    <script src="Scripts/angular.js"></script>
    <script src="Scripts/angular-resource.js"></script>
    <script>
        var IM_Mod_app = angular.module('IM_ng_app', []);
        IM_Mod_app.controller("IM_Ctrl", function ($scope, $http) {
            var PlaId = "DFC";

            $http({
                method: 'GET',
                url: 'http://xxx/api/ItemMaintenance/GetAllFilteredItems',
                params: { PlaId: PlaId }
            }).then(function successCallback(response) {
                $scope.items = response.data;
            }, function errorCallback(response) {            });
        });
    </script>  
</head>

<body ng-app="IM_ng_app">
    <table ng-controller="IM_Ctrl">
        <tr>
            <td>
                @*<select ng-model="itm" size="10" ng-options="itm.ITEM_ID for itm in items" ng-class="{selected: $index==0}" ng-change="onItemSelected(itm.ITEM_ID)">*@
                @*<select ng-model="itm" size="10" ng-options="itm.ITEM_ID for itm in items track by itm.ITEM_ID" ng-selected="$first" >*@
                <select ng-model="itm" size="10" ng-options="itm.ITEM_ID for itm in items track by itm.ITEM_ID"  ng-init="items[0].ITEM_ID">
                <option value="" ng-if="false"></option>
                </select>
            </td>
        </tr>
    </table>
</body>
</html>

Solution

Your ng-init isn't working as you expect because your array does not have any data when the page loads. Instead, it has to complete the $http call before any of the data is available. This just means that you need to finish your work when your $http call comes back, (in the .then).

Your updated AJAX call might look like this

        $http({
            method: 'GET',
            url: 'http://xxx/api/ItemMaintenance/GetAllFilteredItems',
            params: { PlaId: PlaId }
        }).then(function successCallback(response) {
            $scope.items = response.data;

            //Initial the select box
            $scope.itm = $scope.items[0];

            //Get the details 
            getSelectedItemDetails();
        }, function errorCallback(response) {            });

        function getSelectedItemDetails() {
            $http({}) //whatever API endpoint to get the details
                .then(function (response) {
                    // do something with the data.  Maybe extend $scope.itm?
                })
        }

Moving forward, I discourage using ng-init. Instead, just initialize the value of your variables in your javascript. Because of angular's two-way binding, any updates to the value from the javascript will make it to the HTML.