has-children.js

// hard-code that the item will always have children
hasChildren: true

// map the hasChildren property to the hasSubordinates field, serialized from the server
hasChildren: "hasSubordinates"

// compute whether the given item will have children
hasChildren: function(item) {
    return item.hasEmployees && item.relatedDepartment;
}

tree-list-ds-local.js

var dataSource = new kendo.data.TreeListDataSource({
    data: [
        { employeeId: 1, name: 'Montgomery Burns', reportsTo: null, hasSubordinates: true },
        { employeeId: 2, name: "Homer Simpson", reportsTo: 1, hasSubordinates: false },
        { employeeId: 3, name: "Lenford Leonard", reportsTo: 1, hasSubordinates: false }
    ]
});

tree-list-ds-remote.js

var treeListDataSource = new kendo.data.TreeListDataSource({
    transport: {
        read: {
            url: 'api/employees',
            type: 'GET',
            dataType: 'json'
        }
    },
    schema: { /* ... */ }
});

tree-list-ds-schema.js

var treeListDataSource = new kendo.data.TreeListDataSource({
    transport: { /* ... */ },
    schema: {
        // property mapping
        model: {
            id: 'employeeId', // unique id field name
            parentId: 'reportsTo', // relation with another record's id
            hasChildren: 'hasSubordinates', // indicates that there're records that haven't been loaded
            fields: {
            	employeeId: { type: 'number', nullable: false },
                name: { type: 'string', nullable: false },
                reportsTo: { type: 'number', nullable: true }
            }
        }
    }
});