JavaScript and JSON Essentials - Second Edition

Handling asynchronousity using a promise

Though traditionally a callback is the most widely used and often the best way to serve async behavior, it still fails to adhere to some standard requirements for code patterns. A few of the shortcomings faced are as follows:

• If you return any data in callbacks passed to some API library, such as jQuery in the above case, you will never know how the return data in that callback is handled in the code of that library. Consider the code illustrated below :

            $.getJSON('http://localhost:3300/',(jsonData)=>{                console.log("jsonData", jsonData);                return jsonData;            })

The return statement return jsonData; in the previous case makes no sense as to where it goes.

• Another major issue is handling an error exception. ...