Array toString() & String split()

<p>The toString() method returns an array as a comma separated string.</p>
<p id="demo"></p>
<script>
var fruits = ["Banana", "Orange", "Apple", "Mango"];
document.getElementById("demo").innerHTML = fruits.toString();
</script>
// result: Banana,Orange,Apple,Mango

-------------------------------

<script>
function myFunction() {
    var str = "a,b,c,d,e,f";
    var arr = str.split(",");
    document.getElementById("demo").innerHTML = arr[0];
}
</script>

// result: a

If the separator is omitted, the returned array will contain the whole string in index [0].
If the separator is "", the returned array will be an array of single characters.

http://www.w3schools.com/js/js_array_methods.asp 

http://www.w3schools.com/js/js_string_methods.asp