Series of API calls - Server or Client Side?

Series of API calls - Server or Client Side?

I'm working on a web application and I need to do a series of api calls.
One after the only and the following one can't start until the previous
one is finished.
I'm coded the base of my site in Django. Should I do this with javascript
or django?
If django, How do I make a function that waits for the previous task
inside the function to finish? Some tasks could take 2-5 mins
Thanks