I also recently completed my JSON APIs and AJAX session and found it to be too non-educative (for lack of a better word). All I literally did in the last 5 challenges was copy the given code and paste it into the editor. It almost felt like FCC was rushing to the Intermediate Front End Development Projects.
So a frantic search began, to find what I'd missed. But to learn what I'd missed, I had to know what I had actually missed.
The quickest option was to chat with experienced developers in the, well, chat. This is the best comment I had there:
Yes, I feel that that section needs some love.
But all this did was to comfort me. This consoled me that I wasn't the only one having this problem. But, this did not solve my problem. It hadn't even started even solving my problem.
So the quest continued, I even posted this as a question on Quora, but no answer to my avail:
Why is the FreeCodeCamp curriculum for JSON APIs and AJAX so non educative. All it asks to do is paste the given code into the editor?
So, an angry me sent a direct message to Quincy Larson on Quora. In case you're wondering who he is, he is the founder of FreeCodeCamp. Still no reply.
To my rescue came Google, but as I said, to find the answer, I needed to know what I had to search. What should be the magic keyword?
After days of struggling, I finally found that what I need to learn was not APIs (although it requires APIs) but AJAX, which is pretty easy.
After days of searching, Udacity was the angel from heaven.
Here's the link and don't forget to thank me later.
The ultimate source to learn AJAX.