JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app>
    <div ng-controller="Foo as ctrl">Normalized Values:
        <ul ng-repeat="group in groups">{{group.id}}
            <li ng-repeat="item in nomalizedItems(group.id) track by item.id">{{item.id}}:{{item.normalizedValue}}</li>
        </ul>
    </div>
</div>

JavaScript

function Foo($scope) {
    $scope.groups = [{
        id: "group1"
    }, {
        id: "group2"
    }];

    $scope.originalItems = [{
        id: "a",
        groupid: "group1",
        value: 2
    }, {
        id: "b",
        groupid: "group1",
        value: 4
    }, {
        id: "c",
        groupid: "group1",
        value: 6
    }, {
        id: "d",
        groupid: "group2",
        value: 8
    }, {
        id: "e",
        groupid: "group1",
        value: 10
    }];
    $scope.nomalizedItems = function (groupid) {
        var groupItems = $scope.originalItems.filter(function (item) {
            return item.groupid == groupid
        });

        var values = groupItems.map(function (item) {
            return item.value;
        });
        var maxValue = Math.max.apply(null, values);
        return groupItems.map(function (item) {
            return {
                id: item.id,
                normalizedValue: item.value / maxValue
            };
        });
    };
}