while I am trying to copy a object (with nodes) (e.g. cube) to another blend file. The object that I am trying to copy was modified with nodes and I can't copy the object with nodes or manually copy the nodes. Can anyone tell me how to copy the object with nodes and other properties? Or copy the object to another blend file with all of it's modifiers and stuffs. Thanks!
I am assuming you are talking about material nodes etc. If you append the object into the new file, it will bring over anything attached to it automatically such as materials and any node setups associated with it. Use ShiftF1 or go to File > Append and navigate into the blend file as you would a folder, open the Object folder and select the object that you want to copy.
See How can I reuse existing materials, objects, etc from an existing .blend? for more info.
Alternatively, a much faster and easier way is to just copy paste the object directly into the new file by using CtrlC (Copy selection to buffer) and CtrlV (Paste selection from buffer). This will also bring over anything associated with the object.