I took that as my weekend project and started going through the js material available in W3Schools. Since I had already tried my hand at Python, js seemed very easy, just that I have to code between <script> </script>.
Here is what I did (Mind you this is a very very basic use of js, much much more can be done.):
On the left top of this blog (on the header), you will see a “Good <greeting depending on the time of day>.”