The join(...) function has three variations, not counting syntax variations. It joins the elements of a single-index array into a String value.  It may join just the values in the array, or the indexes and values.

Syntax:
join( source-array )
join( source-array, value-separator )
join( source-array, value-separator, index-separator )
source-array.join( )
source-array.join( value-separator )
source-array.join( value-separator, index-separator )

 

 

Parameter	Description
source-array	The original Array value who's elements will be joined  If the array is null, the result will be null.
value-separator	The separator character or characters which will be placed between the values in the source-array.  If null or omitted, a comma will be used. It must be noted that the empty-string is a valid separator.
index-separator	The separator character or characters which will join the index and value of an array element, prior to joining the values using the value-separator.  If the index-separator is null or omitted then the index values will not be included in the result.

 

Example: 
The article titled "The Array Creation Statement" includes an example where dates and events are put into an array and retrieved in sorted order. The for loop in that example could be simplified to a single line by using the join(...) function in place of the for loop. The final 4 lines of that example could be re-written as:

    outStr = usHistory.join("\n", " - ");

It is also possible to do more complicated joins. For instance, the data from the same example could be joined to form an HTML, bulleted list with bold dates by writing

    outStr = "<ul><li><b>"
        + join(usHistory, "</li><li><b>", "</b> ")
        + "</li></ul>";