how to access variables in vuejs data() from js

[FarzinBidokhti]

Hi
In mounted() method i write js function like this:

    data(){
        return {
            selectedEvent: '',
        }
    },
    mounted(){
        $('#trainingevents').on('change',function(){
            var optionsValue = this.options[this.selectedIndex].value;
            var getInputValue = document.getElementById('hiddenInputEvent').value;
            var tmp = document.getElementById('hiddenInputEvent').value = getInputValue + ',' + optionsValue;
            this.selectedEvent = tmp;
        });
    }

this line this.selectedEvent = tmp; not working it return this.selectedEvent not defined. now how can I set value to selectedEvent from jquery change event?
please help me.
Thanks

[chenxch]

Please use arrow functions.

()=>{
var optionsValue = this.options[this.selectedIndex].value;
            var getInputValue = document.getElementById('hiddenInputEvent').value;
            var tmp = document.getElementById('hiddenInputEvent').value = getInputValue + ',' + optionsValue;
            this.selectedEvent = tmp;
}