function testArrayJoin ( ) { { msg ( "testArrayJoin" ) ; let strs = [ 1 , 2 , 3 ] ; let r = "A" + strs . join ( "X" ) ; assert ( r == "A1X2X3" , "join" ) ; } { let strs = [ "a" , "b" , "c" ] ; let r = "B" + strs . join ( "Y" ) ; assert ( r == "BaYbYc" , "joinstr" ) ; } } testArrayJoin ( ) ;