Returns a string consisting of a list of items (as strings) contained by an array. The delimiter character(s) between items is set by the parameter to the method. Note that an array's items are only those items that are accessible via an integer index. Items referenced via string index values are treated as properties of the array object, and are thus independent of integer indexed values (the two sets can coexist in a single array without conflict). The join( ) method works only with the integer-indexed items.