How can I auto-resize a video in HTML?

I currently have this:

<video controls="" autoplay="" name="media"><source src="...." type="video/mp4"></video>

It turns out, that half of the video is cut out of the screen, and I can’t fix it.
Also, if you could help with this too, I’d like to know how to play the video in javascript.

Thanks!

Here is what I tried vs what I am expecting:

>Solution :

You need to add attributes responsible for width and height.

As an example:

<center>
  <video id="Test_Video" width="400" height="240" controls>
    <source src="gfg.mp4" type="video/mp4">
  </video>
</center>

the size is in pixels. If you want you can also specify it in % f.ex width="100%"