JSFiddle - React, Tailwind, and code Playground

HTML

<div data-ng-app="testApp">
    <div data-ng-controller="testCtrl">
        <strong>{{myValue}}</strong>
        <span data-test-directive data-parent-item="myValue" 
            data-parent-update="update()"></span>
    </div>
</div>

JavaScript

var testApp = angular.module('testApp', []);

testApp.directive('testDirective', function ($timeout) {
    return {
        scope: {
            key: '=parentItem',
            parentUpdate: '&'
        },
        replace: true,
        template:
            '<button data-ng-click="lock()">Lock</button>' +
            '</div>',
        controller: function ($scope, $element, $attrs) {
            $scope.lock = function () {
                console.log('directive :', $scope.key);
                
                // Expecting $scope.$parent.pkey to have also been
                // updated before invoking the next line.
                 $scope.parentUpdate();
                 //$timeout($scope.parentUpdate); // would work.
                 console.log('directive :', $scope.key);
            };
        }
    };
});

testApp.controller('testCtrl', function ($scope) {
    $scope.myValue = '1';
    $scope.update = function () {
        // Expecting local variable k, or $scope.pkey to have been
        // updated by calls in the directive's scope.
        console.log('CTRL:', $scope.myValue);
        $scope.myValue = "2";
        console.log('CTRL:', $scope.myValue);
    };
});