I am trying to make a stop watch in js and my code is working correctly until I include Millisecond in my stopwatch.

Here's my code:

index.html
==========

```
<html>
    <head>
        <title>My Second Page</title>
        <script src="script.js"></script>
    </head>
    <body>
        <input type="button" onclick="gettime()" value="Start Stopwatch"></a>
    </body>

</html>

```

script.js
=========

```
 var ss = 0,
    mm = 0,
    hh = 0,
    ms = 0;
var once = 0;

function gettime() {
    if (once == 0) {
        document.write('<h1 id="stopwatch"></h1>');
        once++;
    }
    setInterval("msss()", 100);
}

function msss() {   // I have defined msss

    printtime();
    if (ms > 1000) {
        sec();
    } else {
        ms += 100;
    }

}

function sec() {
    ms = 0;
    printtime();
    if (ss > 59) {
        min();
    } else {
        ss += 1;
    }
}

function min() {
    ss = 0;
    printtime();
    if (mm > 59) {
        hr();
    } else {
        mm += 1;
    }
}

function hr() {

    mm = 0;
    printtime();
    hh += 1;
}

function printtime() {
    document.getElementById('stopwatch').innerHTML = 'H: ' + hh + 'M: ' + mm + ' S: ' + ss + ' MS: ' + ms;
}

```

**Error Code**

> 
> ReferenceError: msss is not defined
> 
> 
> 

What am I doing wrong?