Array data display in list / span Array with id for single items

Array data display in list / span
Array with id for single items

<h2>JavaScript Arrays</h2>

<p id="demo"></p>

<script>
n = 0;
var cars = ["Saab", "Volvo", "BMW"];

var str = "";
for (var i = 0; i < cars.length; i++)
{
n = n + 1;
str = str + "<span id='" + n +"'>this car is:" + cars[i] + "</span><br>";

//str += "<li>" + cars[i] + "</li>";

//document.write("this car name is :" + cars[i] + "<br>");
 }

document.getElementById("demo").innerHTML = str;

</script>