BF tempalte
And now, the BF template. The data.Add(...) or data[...]=... parts have been encoded in a quick and dirty way
Note that we need to start our code far from memory initial cell, to leave some space needed for code to decimal printing
/** HEADERS **/
>>>>>>>>>>>>>>>> 16 empty cells
/** DATA **/
++++++++++++++++++++++++++++++++++ B
++++++++++++++++++++++++++++++++> ** part 2**
++++++++++++++++++++++++++++++++++++ F
++++++++++++++++++++++++++++++++++> ** part 2**
>
/** BF code goes here **/
>
++++++++++++++++++++++++++++++++++ C
+++++++++++++++++++++++++++++++++> ** part 2**
++++++++++++++++++++++++++++++++++++++++++ S
+++++++++++++++++++++++++++++++++++++++++> ** part 2 **
>
/** CS code goes here **/
>
++++++++++++++++++++++++++++++++++++++ J
++++++++++++++++++++++++++++++++++++> ** part 2**
++++++++++++++++++++++++++++++++++++++++++ S
+++++++++++++++++++++++++++++++++++++++++> ** part 2 **
>
/** JS code goes here **/
>
/** CODE **/
,>++++++++[-<-------->]+<--- read input; set else flag; test if=C
[------- not C: test J
[[-]>-< not J: default case (BF)
/** BF headers block goes here **/
<[<]>[.>]<[[-]<] print BF headers
<<[[<]<] go 2 cells before map
<++++++++[->+++++>++++++++<<]>+++>-- generate 43 and 62
>[ for each map entry or key
[[-<<<+>.>>]<.[->+<]<[->+<]>>>] write 43 and 62 as needed and move these values
<.[->+<]<[->+<]>>>] process next map entry or key
<[-]<[-]<<<[[<]<]>>[>]>[.>] print BF code
>[[>]>]>>> go back to loop original position
]>[-< J (so JS)
/** JS headers block goes here **/
<[<]>[.>]<[[-]<] print JS headers
<<[[<]<]>> go to first map entry
[ for each entry
<<++++++++[->++++<]>.+[-<+++>]<+.--- data addition syntax in JS
.+++++++++++++++++++.--------------- ** part 2 **
----.------.[-]+++++[->++++++++<]>-. ** part 3 **
[-]>[.[-<<<<<<<<<<<<<<+>>>>>>>>>>>>>>]>]key (leave space for code to decimal conversion)
+++++[-<++++++++>]<-.--------[->+++< data addition syntax in JS after key
]>.[---<++>]<-.-[-->+++<]>+. ** part 2 **
[-]>[ value
[-<<<<<<<<<<<<+<<+>>>>>>>>>>>>>>] print each decimal code
<<<<<<<<<<<<[>>>>++++++++++<<<<[-> ** with a comma **
+>>+>-[<-]<[->>+<<<<[->>>+<<<]>]<<] ** if there is another number **
>+[-<+>]>>>[-]>[-<<<<+>>>>]<<<<]<[> ** continued **
++++++[<++++++++>-]<-.[-]<]>>>>>>> ** continued **
>>>>>>+>[<++++++[-<++++++>]<++.[-]> ** continued **
]<[-<]>> ** continued **
] end of value
++++[-<++++++++>]<-[-<+++>]<.[--->++< data addition syntax in JS after value
]>---.[-]++++++++++.[-]>> ** part 2 **
] map creation is over
<<<<<<<<<<<<<<<<[<]>[.>] print JS code
>>>>>>>>>>>>>>> go back to loop original position
>]<]>[- C (so CS)
/** CS headers block goes here **/
<[<]>[.>]<[[-]<] print CS headers
<<[[<]<]>> go to first map entry
[ for each entry
<<++++++++[->++++<]>........+[-<+++>] data addition syntax in CS
<+.---.+++++++++++++++++++.---------- ** part 2 **
---------.-----[-->+<]>.++[---<++++>] ** part 3 **
<+.+[-->+++<]>+..[--<+>]<----------.- ** part 4 **
-----.[-]>> ** part 5 **
[.[-<<<<<<<<<<<<<<+>>>>>>>>>>>>>>]>] key (leave space for code to decimal conversion)
++++++++[-<++++>]<++.++++++++++.----- data addition syntax in CS after key
-------.+++++[->+++<]>-.---------.+++ ** part 2 **
+++++++++++++++.+[----<+>]<++.+++[->+ ** part 3 **
++<]>.+++++.++++++.[----<+++>]<++++.+ ** part 4 **
+.[--->++++<]>-. ** part 5 **
[-]>[ value
[-<<<<<<<<<<<<+<<+>>>>>>>>>>>>>>] print each decimal code
<<<<<<<<<<<<[>>>>++++++++++<<<<[-> ** with a comma **
+>>+>-[<-]<[->>+<<<<[->>>+<<<]>]<<] ** if there is another number **
>+[-<+>]>>>[-]>[-<<<<+>>>>]<<<<]<[> ** continued **
++++++[<++++++++>-]<-.[-]<]>>>>>>> ** continued **
>>>>>>+>[<++++++[-<++++++>]<++.[-]> ** continued **
]<[-<]>> ** continued **
] end of value
+++++[-<+++++>]<[->+++++<]>.--[---<+> data addition syntax in JS after value
]<.-[--<+++>]<-.[-]++++++++++.[-]>>> ** part 2 **
] map creation is over
<<<<<<<<<<<<<<<<[<]<[<]<[<]>[.>] print CS code
>>>>>>>>>>>>>>>>>>>>>>> go back to loop original position
] the end
Minified version
/** HEADERS **/>>>>>>>>>>>>>>>>/** DATA **/+++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>/** BF code goes here **/>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>
>/** CS code goes here **/>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++>>/** JS code goes here **/>/** CODE **/,>++++++++[-<-------->]+<---[-------[[-]>-</*
* BF headers block goes here **/<[<]>[.>]<[[-]<]<<[[<]<]<++++++++[->+++++>++++++++<<]>+++>
-->[[[-<<<+>.>>]<.[->+<]<[->+<]>>>]<.[->+<]<[->+<]>>>]<[-]<[-]<<<[[<]<]>>[>]>[.>]>[[>]>]>>
>]>[-</** JS headers block goes here **/<[<]>[.>]<[[-]<]<<[[<]<]>>[<<++++++++[->++++<]>.+
[-<+++>]<+.---.+++++++++++++++++++.-------------------.------.[-]+++++[->++++++++<]>-.[-]>
[.[-<<<<<<<<<<<<<<+>>>>>>>>>>>>>>]>]+++++[-<++++++++>]<-.--------[->+++<]>.[---<++>]<-.-[-
->+++<]>+.[-]>[[-<<<<<<<<<<<<+<<+>>>>>>>>>>>>>>]<<<<<<<<<<<<[>>>>++++++++++<<<<[->+>>+>-[<
-]<[->>+<<<<[->>>+<<<]>]<<]>+[-<+>]>>>[-]>[-<<<<+>>>>]<<<<]<[>++++++[<++++++++>-]<-.[-]<]>
>>>>>>>>>>>>+>[<++++++[-<++++++>]<++.[-]>]<[-<]>>]++++[-<++++++++>]<-[-<+++>]<.[--->++<]>-
--.[-]++++++++++.[-]>>]<<<<<<<<<<<<<<<<[<]>[.>]>>>>>>>>>>>>>>>>]<]>[-/** CS headers block
goes here **/<[<]>[.>]<[[-]<]<<[[<]<]>>[<<++++++++[->++++<]>........+[-<+++>]<+.---.+++++
++++++++++++++.-------------------.-----[-->+<]>.++[---<++++>]<+.+[-->+++<]>+..[--<+>]<---
-------.------.[-]>>[.[-<<<<<<<<<<<<<<+>>>>>>>>>>>>>>]>]++++++++[-<++++>]<++.++++++++++.--
----------.+++++[->+++<]>-.---------.++++++++++++++++++.+[----<+>]<++.+++[->+++<]>.+++++.+
+++++.[----<+++>]<++++.++.[--->++++<]>-.[-]>[[-<<<<<<<<<<<<+<<+>>>>>>>>>>>>>>]<<<<<<<<<<<<
[>>>>++++++++++<<<<[->+>>+>-[<-]<[->>+<<<<[->>>+<<<]>]<<]>+[-<+>]>>>[-]>[-<<<<+>>>>]<<<<]<
[>++++++[<++++++++>-]<-.[-]<]>>>>>>>>>>>>>+>[<++++++[-<++++++>]<++.[-]>]<[-<]>>]+++++[-<++
+++>]<[->+++++<]>.--[---<+>]<.-[--<+++>]<-.[-]++++++++++.[-]>>>]<<<<<<<<<<<<<<<<[<]<[<]<[<
]>[.>]>>>>>>>>>>>>>>>>>>>>>>>]
