Did Mosh forget to add some code lines?

JavaScript
1

In The Ultimate JavaScript Mastery Series - Part 2 > lesson 14, stopWatch exercise, I had literally copy the solution code to my vs code, but nothing happen when I execute the code by
const sw = new StopWatch
sw.start() and the other methods?
I think there is missing some maybe console.logs, and code more

2

share the code? or screenshot it

3

function Stopwatch() {
let startTime, endTime, running, duration = 0;

this.start = function() {
if (running)
throw new Error(‘Stopwatch has already started.’);

running = true; 

startTime = new Date();

};

this.stop = function() {
if (!running)
throw new Error(‘Stopwatch is not started.’);

running = false; 
  
endTime = new Date();

const seconds = (endTime.getTime() - startTime.getTime()) / 1000;

};

this.reset = function() {
startTime = null;
endTime = null;
running = false;
duration = 0;
};

Object.defineProperty(this, ‘duration’, {
get: function() { return duration; }
});
}