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In a previous blog post, I showed how to create your first cloud function (plus a video). It’s very likely that your cloud function will need to invoke an external REST API. The following tutorial will show you how to create such a function (it’s very easy).

1. Sign into an IBM Cloud account
2. Click Catalog
3. Remove the label:lite filter and type
4. Click on Functions box
5. Click the Start Creating button
6. Click Create Action
7. For Action Name, enter "ajoke" and click the Create button. A new cloud function will be created with Hello World message
8. Replace the function code with the following code which invokes a 3rd party REST API which returns a random joke:

   
   var request = require("request");
   
   function main(params) {
      var options = {
         url: "https://api.icndb.com/jokes/random",
         json: true
      };
   
      return new Promise(function (resolve, reject) {
         request(options, function (err, resp) {
            if (err) {
               console.log(err);
               return reject({err: err});
            }
         return resolve({joke:resp.body.value.joke});
         });
      });
   }
   

   • The code is simple. It uses the request Node.js package to connect to an external REST API
   • The external REST API returns a random joke
   • A JavaScript Promise is used for invoking the REST API
   • At the end, the cloud function returns a response in JSON format
9. Now click the Save button to save the code. Once the code is saved, the button will change to Invoke. Click the button to invoke the function. In the right-hand panel you should see output with a random joke:

   {
     "joke": "Project managers never ask Chuck Norris for estimations... ever."
   }

This is how it looks inside the IBM Cloud Functions editor:

Source: DZone