Before we use Javascript (or any other programming/scripting language) with an API it may be useful to explore its capabilities first in a tool that allows us to do so quickly.

Examining the top of the imgur API documentation, we can see at the top right that it can be explored in the Postman tool. Postman allows you to set the method, headers, and request data from a graphical interface.

If you are more of a text person, the cUrl tool (available on many platforms) will let you test and explore the API from the command line. You can pass the following switches:

--request   the HTTP method
--url       the URL to access
--header    a HTTP header in name:value format (pass any number of them)
--form      a FormData-like element in name=value format (any number of them) 
--data      send request data in the format expected by the server

As you see in the imgur API documentation, it exemplifies accesses via cURL by default. You can get the respective access for jQuery, Java, Python, node.js, etc.