Javascript Date Format and Date Difference

I am using the below javascript to display the data from the table. How to format the date and find the difference between two dates.

<script type="text/javascript">
    $(function () {

        var table = $('.data-table').DataTable({
            processing: true,
            serverSide: true,
            ajax: {
                url: "{{ route('job.jobhistory.index') }}",
                data: function (d) {
                    d.job_status_name = $('#job_status_name').val(),
                        d.search = $('input[type="search"]').val()
                }
            },
            columns: [{
                    data: 'job_enq_number',
                    name: 'job_enq_number'
                },
                {
                    data: 'job_cust_name',
                    name: 'job_cust_name'
                },
                {
                    data: 'job_cust_mobile',
                    name: 'job_cust_mobile'
                },
                {
                    data: 'job_item_type',
                    name: 'job_item_type'
                },
                {
                    data: 'job_item_brand',
                    name: 'job_item_brand'
                },
                {
                    data: 'job_type',
                    name: 'job_type'
                },
                {
                    data: 'job_enq_date',
                    name: 'job_enq_date'

                },
                {
                    data: 'job_ins_date',
                    name: 'job_ins_date'
                },
                {
                    data: 'job_work_date',
                    name: 'job_work_date'
                },
                {
                    data: 'job_completed_date',
                    name: 'job_completed_date'
                },
                {
                    data: 'job_invoice_date',
                    name: 'job_invoice_date'
                },
                {
                    data: 'job_invoice_number',
                    name: 'job_invoice_number'
                },

                {
                    data: 'job_status_name',
                    name: 'status'
                },
            ]
        });

        $('#job_status_name').change(function () {
            table.draw();
        });

    });

</script>