7 kyu Simple Fun #252: Parking Cost.js

/*
Description:
Task
A new parking lot just opened in your city. Its rates are: ```

The first 30 minutes (inclusive) of parking are free;
From 31 minutes to 2 hours, every 10 minutes costs $1;
Every 10 minutes over 2 hours costs $2.``` Since you are charged for every 10 minutes, you should round the number of minutes spent in the parking lot up to the nearest multiple of 10. For example, if you've been in the parking lot for 43 minutes, you will pay for 50 minutes.
You are given 2 strings: The time you typically arrive at your usual parking lot, and the time you typically leave it. Now you want to know how much you'll have to pay at the new parking lot.

If timeOut is earlier than timeIn, you can assume that timeOut is on the next day.

Input/Output
[input] string timeIn

The time you usually arrive at the parking lot, in the format hh:mm.

[input] string timeOut

The time you usually leave the parking lot, in the format hh:mm.

[output] an integer

The number of dollars you'll need to pay.

Example
For timeIn = "14:11" and timeOut = "14:39", the output should be 0.

You usually spend 28 minutes in the parking lot, so you won't have to pay anything.

For timeIn = "07:02" and timeOut = "07:42", the output should be 1.

You spend 40 minutes in the parking lot, so you'll need to pay for the first 10 minutes after the free half hour.

For timeIn = "12:20" and timeOut = "14:54", the output should be 17.

You spend 2 hours and 34 minutes in the parking lot, so you'll need to pay $9 for the first 2 hours (there are 90 minutes between 30 minutes and 2 hours, each 10 minutes of which cost $1) and 4 * 2 = $8 for the next 34 minutes, for a total of 8 + 9 = 17.

For timeIn = "23:50" and timeOut = "00:30", the output should be 1.

You spend 40 minutes in the parking lot, so you'll need to pay for the first 10 minutes after the free half hour.
*/
function parkingCost(timeIn, timeOut) {
  const tI = timeIn.split(":");
  const tO = timeOut.split(":");
  let time = new Date(new Date(0,0,0,tO[0],tO[1])-new Date(0,0,0,tI[0],tI[1]))
  time = time.getHours()*60+time.getMinutes();
  return (time <= 30) ? 0 : (time <= 120) ? Math.ceil((time-30)/10) : 9+(Math.ceil((time-120)/10))*2
}