The ngStyle directive allows you to set CSS style on an HTML element conditionally.

@example

    <span ng-style="{color:'red'}">Sample Text</span>

@NgDirective(
   selector: '[ng-style]',
   map: const { 'ng-style': '@styleExpression'})
class NgStyleDirective {
 dom.Element _element;
 Scope _scope;

 String _styleExpression;

 NgStyleDirective(dom.Element this._element, Scope this._scope);

 Function _removeWatch = () => null;
 var _lastStyles;

/**
 * ng-style attribute takes an expression hich evals to an
 *      object whose keys are CSS style names and values are corresponding values for those CSS
 *      keys.
 */
 set styleExpression(String value) {
   _styleExpression = value;
   _removeWatch();
   _removeWatch = _scope.$watchCollection(_styleExpression, _onStyleChange);
 }

 _onStyleChange(Map newStyles) {
   dom.CssStyleDeclaration css = _element.style;
   if (_lastStyles != null) {
     _lastStyles.forEach((val, style) { css.setProperty(val, ''); });
   }
   _lastStyles = newStyles;

   if (newStyles != null) {
     newStyles.forEach((val, style) { css.setProperty(val, style); });
   }
 }
}