AngularJS $ timeout is executed immediately in safari

Question

AngularJS $ timeout is executed immediately in safari

I am having a weird problem with $timeout

in AngularJS that only occurs in Safari (both iOS and macOS) but not in other browsers. Instead of waiting for the specified milliseconds, Safari performs this function immediately. All the code is available here , but this is the relevant part of the code:

app.directive('upload', ['$lhttp', '$http', '$interval', '$timeout', '$q', '$location', function ($lhttp, $http, $interval, $timeout, $q, $location) {
    return {
      templateUrl: '/.src/views/upload-widget.html',
      controller: function($scope, $element, $attrs) {
      // code ...

      // Define upload function
      vm.uploadFiles = ()=>{
        // code ...

        // Create the payload for the upload request
        let formdata = new FormData();
        formdata.append("salt", salt);
        // code ...

        // Create the upload request
        let request = $http({
          method: 'POST',
          url: "/.src/php/upload.php",
          data: formdata,
          transformRequest: angular.identity,
          uploadEventHandlers: {
            progress: function(e) {
              vm.progress = Math.round((e.loaded/e.total)*100) + "%";
              if (vm.progress === '100%') vm.get_server_progress(salt);
            }
          },
          headers: {'Content-Type': undefined}
        });

        // Create handler functions for success and errors
        request.then(function successCallback (response) {
          vm.server_progress = "100%";
          vm.actually_loading = false;
          $timeout(()=>{ vm.loading = false }, 600);
          if (response.data.error.length) {
            vm.fail = true;
            vm.error_message = response.data.error;
          }
          if (!response.data.log.length) {
            vm.fail = true;
            vm.error_message = $scope.m.text.upload_error;
          }
        }, function errorCallback (response) {
          // code ...
        });
      }

      // code ...

      // Create function for checking status of server side processing of the upload
      vm.get_server_progress = (salt)=>{
        $http.get('/.src/php/status.php?salt='+salt+'&d='+Date.now()).success((data)=>{
          vm.server_progress = data+"%";
          re_get_progress_if(salt);
        }).error(()=>{
          re_get_progress_if(salt);
        });
      }

      function re_get_progress_if (salt) {
        //////////////////////////////////////
        // THIS IS THE PROBLEMATIC $TIMEOUT://
        if (vm.actually_loading) $timeout(vm.get_server_progress, 100, true, salt);
      }
    },
    controllerAs: 'up'
  };
}]);