Check age using Date object in JS Code Answer

I need help with the Date object in JS. I need a return that checks if the patient is an adult based on the DOB. I am unsure how to go about using the date object to get a return of age in milliseconds (Date returns milliseconds since 1 January 1970 UTC). If anyone has an idea, I appreciate it. <3

 let today = Date.now()
 function patient(fname, lname, origin, dob){
    this.fname,
    this.lname,
    this.origin,
    **this.dob,**
    this.age = (today - dob)
    this.isAdult = age > 18)}

Answer

You can convert your DOB to milliseconds since Epoch time with getTime()

for dob, you can set the input variables to be month, day, and year, make a new Date object, and use getTime() to convert it to milliseconds:

 function patient(fname, lname, origin, month, date, year){
    this.fname,
    this.lname,
    this.origin,
    this.dob = new Date(`${month} ${day}, ${year}`).getTime()
    this.age = (Date.now() - dob)/1000/60/60/24/365 
    //convert to seconds/minutes/hours/day/year (ignoring leap years for this examples)
    this.isAdult = age > 18)}

Link to CodePen example

Now it’s just a matter to convert milliseconds back to year, the example above ignores the leap year, depending on the accuracies you going for you can round it up, or write a function to determine the exact numbers down to decimals