Introduction
Ok so, here’s the thing. Typically, roblox doesn’t allow you to use their own API from roblox. You’ll have to get a little bit hacky with JavaScript.
Fortunately enough, there’s a website for FREE JavaScript app hosting. It’s called glitch. You can do this very simply using a library called request and the built in node.js library called http.
Setting It Up
First, once you’ve signed up: Create a new hello-express app.
Secondly, clear out the server.js and go to package.json.
Once you’re in package.json, you will want click Add Package.
Search “request” and click it. It should install. Once you’ve done that, you should delete the folders called “/views” and “/public”.
Adding Packages
JavaScript Code
You can now type this code into the file called server.js
const http = require("http");
const request = require("request");
http.createServer((req, res) => {
try {
let url = request.get("https://www.roblox.com" + req.url);
url.on("response", response => {
if (response && response.headers) {
url.pipe(res);
}
});
} catch (e) {
res.write(e);
res.end();
}
}).listen(process.env.PORT, () => console.log("listening on " + process.env.PORT))
Done! Now you can go to https://yourapp.glitch.me/catalog/json (replace yourapp with the name of your app)
and you can view the api of the catalog!
Alternatively, you can use my app for this and copy it: app link
Roblox End
On roblox, you can use HttpService on the client and get the items on the server. Keep in mind, I’m on mobile so I can’t show you what it will look like.
local HttpService = game:GetService("HttpService")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteFunction = ReplicatedStorage:WaitForChild("RemoteFunction") -- change the name to your liking, also don't forget to create a RemoteFunction
local appName = "robloxdevforumproxy" -- replace it with your app
local baseUrl = "https://" .. appName .. ".glitch.me/catalog/json"
function RemoteFunction.OnServerInvoke()
return HttpService:JSONDecode(HttpService:GetAsync(baseUrl))
end
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteFunction = ReplicatedStorage:WaitForChild("RemoteFunction") -- change the name to your liking, also don't forget to create a RemoteEvent
local CatalogApi = RemoteFunction:InvokeServer() -- returns a list, use this to duplicated ui elements to your liking.
local GearFrame = script.Parent.GearFrame
Conclusion
Anyways, you can learn about the catalog api here:
Feel free to ask me any questions if you have any! 
