Any api key on the client will be noticeable, there is really no way to hide it. Usually the server gets the data, and then sends the code to the browser with the data already there. The purpose of hiding the key is so others can’t steal it. If other’s get your key, they can use it to request data from the API - costing you more money as you only get so many requests for data or the company charges you more. As mentioned above you don’t really need to hide the key if its free because thieves aren’t interested in it.
If for some reason you absolutely have to, and to answer your question, you can do so easily by making your own api for the api:
To add to the Glitch suggestion that @IsaacAbrahamson mentioned, @deuscode actually did just that last week! Have a look at this post and scroll down to the fifth post for a Glitch template that can be easily remixed!