The toString() method can be used to convert an array into a string. It returs a result containing string and it will seperate the different elements in the array with commas.

var group = ['one','two','three','four'];

var conv = group.toString();

The same thing can also be done by valueOf() method in javascript.

var group = ['one','two','three','four'];

var conv = group.valueOf();

To convert comma seperated value to an array, split() method is used. It is used to seperate a string into array that contains substrings and also returns a new array.

Syntax:

var group = ['one','two','three','four'];

var conv = group.valueOf();

Seperator:  It can contain a regular expression or a character to split the string.
Limit:  It defines the number of splits
 

var group = ['one','two','three','four']

var conv = "one,two,three,four"

var groupArray = conv.split(",") //print groupArray[0] one.