Some initiation data in the HTMLWriter with embed_frames=True is not set to "zero" when the same writer is used another time. So the following code

writer=HTMLWriter(fps=1, embed_frames=True)
anim1.save('anim1.html', writer)
anim2.save('anim2.html', writer)

would result in an anim2.html animation that starts with the anim1 animation.

This pr move the initiation from __init__ to setup to avoid that problem.

It also set the correct Nframes in the embeded case. This doesn't seems to be necessary but it seems better and clearer when the variable is there. The only thing I think it does is to set

var frames = new Array(Nframes)

and Nframes=0 seems to work . I don't know javascript so I don't know if there are any important difference if the length of the Array is set before it is used or not.

I also deleted a variable that is not used anywhere.

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way