Javascript Error Message When Adding Milliseconds To A Clock

I keep getting this error message: Uncaught SyntaxError: Unexpected identifier when adding milliseconds to a clock. I am copying it out of a book, so I am not sure what is wrong.

Solution 1:

Looks like you're missing a + here:

document.write(hours + ":" + minutes + ":" + seconds + ":" mil);
//--------------------------------------------------------^^^^

Solution 2:

The line

document.write(hours + ":" + minutes + ":" + seconds + ":" mil);

should read

document.write(hours + ":" + minutes + ":" + seconds + ":" + mil);

There is a + missing before mil

Solution 3:

you missed a +

document.write(hours + ":" + minutes + ":" + seconds + ":" + mil);