Declaring variables breaks code

JavaScript
1

I have narrowed down the problem of my code to one line, which is where I declare the variables. This is the working code:

function Stopwatch() {

  let active = false;

  let duration = 0;

  let startTime = 0;

  let endTime = 0;

    this.start = function () {

        if (active) {

            throw new Error('Stopwatch has already started');

        }

        startTime = new Date();

        active = true;

    };

    this.stop = function () {

        if (!active) {

            throw new Error('Stopwatch is not started')

        }

        endTime = new Date();

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

        duration += seconds;

        active = false;

    };

    this.reset = function () {

        clearInterval(timer);

        active = false;

        duration = 0;

    };

    Object.defineProperty(this, 'duration', {

        get: function () { return duration; }

    });

}

const sw = new Stopwatch();

and this is the code that’s not working:

function Stopwatch() {

  let active = false;

  let duration, startTime, endTime = 0;

    this.start = function () {

        if (active) {

            throw new Error('Stopwatch has already started');

        }

        startTime = new Date();

        active = true;

    };

    this.stop = function () {

        if (!active) {

            throw new Error('Stopwatch is not started')

        }

        endTime = new Date();

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

        duration += seconds;

        active = false;

    };

    this.reset = function () {

        clearInterval(timer);

        active = false;

        duration = 0;

    };

    Object.defineProperty(this, 'duration', {

        get: function () { return duration; }

    });

}

const sw = new Stopwatch();

The only difference is how I declare the variables, if I do it on one line, it fails, but declare them on one line separately it works. What is happening?

Thanks

2

The problem is that when I run sw.duration I get undefined with my code.

3

OK, so let active, startTime, endTime, duration = 0; works because only duration is set a value. The other variables aren’t assigned a value.

4

let duration = 0,
startTime = 0,
endTime = 0;