Q:

How do you get the mouse hovered label value with the highcharts custom event plugin? 

I am using highchars.js and the custom-event plugin. 
I add a mouseover event handler on the xAxis label.  How can I get the hovered label value in the event handler?  Thanks. 
https://jsbin.com/havezujuva/edit?html,js,output
xAxis: {
            categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'],

            labels:{
                events: {
                    mouseover: function (e) {
                        console.log('over');
                    }
                }               
            }

        }

A:

You can access it from this.axis.categories[this.value].  
xAxis: {
        categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'],

        labels:{
            events: {
                mouseover: function (e) {
                    console.log('over');
                    console.log(this.axis.categories[this.value]);
                }
            }               
        }

    }

