JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app ng-controller="Test">
    1. <input ng-model="prop" /><br />
    2. <input ng-model="shadowProp" />
</div>

JavaScript

function Test ($scope) {
    $scope.prop = $scope.shadowProp = ''
    
    $scope.$watch('prop', function () {
        if (/^[^\d]+$/.test($scope.prop)) {
            $scope.shadowProp = $scope.prop
        }
    })
    
    $scope.$watch('shadowProp', function () {
        $scope.prop = $scope.shadowProp
    })
}