JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app="myApp"
    <div ng-controller="myCtrl">
        <input type="text" ng-model="myDate"> <small>Format: YYYYMMDD</small>
        <p>
        {{myDate | myFormatDateFilter}}
        </p>
    </div>
</div>

CSS

small { color: #999; }

JavaScript

angular.module('myApp',[])
    .controller('myCtrl',function($scope){
        $scope.myDate = '20131115';
        
        $scope.$watch('myDate',function(val){
            $scope.myDate = val.replace(/[^0-9]/gi,'');
            if(val.length > 8)
                $scope.myDate = val.slice(0,8);
        });
    })
    .filter('myFormatDateFilter',function(){
        return function(input){
            if(angular.isDefined(input)){
                if(input.length >= 8){
                    input = input.slice(0,8);
                    
                    input = input.slice(4,6) + '/' + input.slice(6,8) + '/' + input.slice(0,4);
                }
                /*
                if(input.length >= 4)
                    input = input.slice(0,4) + '/' + input.slice(4);
                if(input.length >= 7)
                    input = input.slice(0,7) + '/' + input.slice(7);
                */
            }
            return input;
        };
    });