dont support node 8!

[LFF5644]

this is not the syntax supported in node 8!
if u want to make it node 8 compertible use let returned=undefined;

rtjscomp/rtjscomp.js

Line 1409 in 1e75767

let returned;

[L3P3]

if you tested it and it fixes it, please do pr (put #58 in desc and commit name!), also with increasing last version number in package.json