triggerValidation() {
		if (typeof(this.vfunc) != 'function')
			return false;

		const wasValid = this.isValid();

		this.vfunc();

		return (wasValid != this.isValid());
	}
Force validation of the current input value.

Usually input validation is automatically triggered by various DOM events
bound to the input widget. In some cases it is required though to manually
trigger validation runs, e.g. when programmatically altering values.

@instance
@memberof LuCI.ui.AbstractElement