Hey :), js.lib.Object should exist, it was added in haxe 4 – perhaps you’re using haxe 3 where the project needs haxe 4?
Could you share your build.hxml also?
Hey 
I’m using haxe 4.1.5 lime 7.8.0 and openfl 9.0.2
do I have to change some configuration of the file? I updated the libraries later
It’s possible it’s not set to compile to js or something in the config. Is there any way for me to try your project here so I can see if it work for me?
It shouldn’t be possible though, since only std/js/_std/haxe/ds/StringMap.hx has import js.lib.Object.
Or did you (or one of your lib) copy this file to another place?
I suppose you’re not targetting js when you get this error?
We need a bit more information to help what work out what’s going wrong
What happens if you open a cmd window and run haxe? Do you see Haxe Compiler 4.1.5 ... ?
What happens if you try to run haxe build.hxml on your project? Does it work there and but not in your editor?