labelFormatter : Function

var  chart =  new  CanvasJS.Chart("container",
{
 .
 .
 axisY:{
       crosshair: 
	{
		enabled: true,
		labelFormatter: function ( e ) {
			return "Custom Point"  + e.value;  
		} 
	}      
  },
 
 .
 . 
});
chart.render();

• By using labelFormatter, you can return any value to be displayed as crosshair’s label.
  Below is the structure of object passed as parameter to the function

  e: { // parameter sent to function
         chart,
         axis,
         crosshair,
         value       
   }
  

  Note If you have to access any preset options of the chart, you can access them via e.chart.options. For example e.chart.options.title.text