问如何避开大内容的角度性能问题

EN

app.directive('bigText', function () {
  return {
    scope: {
      bigText: '='
    },
    template: '<textarea>',
    link: function (scope, element) {
      // .val(value) on directive init
      var initialized = false;
      // prevents .val(oldValueFromOutside) on input
      var internalChange = false;
      var $textarea = element.find('textarea');

      scope.$watch('bigText', function (oldVal, newVal) {
        if (internalChange || (initialized && oldVal === newVal)) return;
        initialized = true;
        $textarea.val(newVal);
      });

      // generic JS debounce,
      // for ex. https://github.com/niksy/throttle-debounce
      var handler = debounce(1000, function () {
        var text = $textarea.val();
        if (scope.bigText !== text) {
          internalChange = true;
          scope.$apply(function () {
            scope.bigText = text;
          });
          internalChange = false;
        }
      });
      $textarea.on('change keyup', handler);
      // $textarea.off on scope destroy
    }
  };
});