code: function ScalifyFilter($filter) {
    const numberFilter = $filter('number');
    const filterFn = function(scale) {
      const text = numberFilter(scale, 0);
      return text ? `1\u00a0:\u00a0${text}` : '';
    };
    filterFn['$stateful'] = true;
    return filterFn;
  }
docs: Format a number as a localized scale.
  For instance:
  - For 'fr-CH' the value 25000 will become '1 : 25 000'.
  - For 'en-US' the value 25000 will become '1 : 25,000'.
  
  Example:
  
  <p>{{25000 | ngeoScalify}}</p>
  
  
  @param {angular.IFilterService} $filter Angular filter
  @return {function(number): string} A function to format number into a 'scale'
  string.
  @ngInject
  @ngdoc filter
  @ngname ngeoScalify