URGENT!- hourly leave

Hello,

I want to add hourly leave to leave application module on Erpnext. I write the code as below, but it does not calculate. Can you help me?

frappe.ui.form.on(“Leave Application”, {
from_date(cur_frm) {
cur_frm.calculate_hourly_leave();
},

 to_date(cur_frm) {
     cur_frm.calculate_hourly_leave();
 }

});

cur_frm.calculate_hourly_leave = function() {
var a = moment(cur_frm.doc.from_date);
var b = moment(cur_frm.doc.to_date);

 console.log(a.diff(b, 'minutes'))
 console.log(a.diff(b, 'hours'))
 console.log(a.diff(b, 'days'))
 console.log(a.diff(b, 'weeks'))
 //var total_leave_hours = cur_frm.total_leave_hours;

}