Increase the check variable by one, each time the header is twofold clicked:
Definition and Usage
ng-dblclick mandate instructs AngularJS when a HTML
component is twofold clicked.
ng-dblclick mandate from AngularJS won't abrogate the component's unique ondblclick occasion,
both are executed.
Supported by all HTML elements.
|expression||An articulation to execute when a component is cdouble-licked.|