Here is the code example that helps you.

    // JavaScript program to illustrate 
    // calculation of no. of days between two date 
  
    // To set two dates to two variables
    var date1 = new Date("06/30/2019");
var today = new Date();
  
// To calculate the time difference of two dates
var Difference_In_Time = today.getTime() - date1.getTime();
  
// To calculate the no. of days between two dates
var Difference_In_Days = Difference_In_Time / (1000 * 3600 * 24);
  
//To display the final no. of days (result)
document.write("Total number of days between dates  <br>"
               + date1 + "<br> and <br>" 
               + today + " is: <br> " 
               + Difference_In_Days);