You want to convert an array to a string.
Use the join( ) method.
ActionScript provides you with a built-in way to quickly convert arrays to strings (assuming, of course, that the array elements themselves are either strings or another datatype that ActionScript can automatically cast to a string) using the join( ) method. You should provide the join( ) method with a parameter that tells Flash which delimiter to use to join the elements:
myArray = ["a", "b", "c"]; trace(myArray.join("|")); // Displays: a|b|c
If you don't provide a delimiter, Flash uses a comma by default:
myArray = ["a", "b", "c"]; trace(myArray.join( )); // Displays: a,b,c