Introduction to JavaScript Object Notation

Chapter 4. JSON Schema

In Chapter 3, we covered the JSON data types. The importance and usefulness of data types was discussed. Knowing ahead of time what something is and what it is for (remember the kid with the hammer) makes a world of difference.

In most scenarios with data interchange formats, the data is being created to send across the Internet or a network to another party. That party usually has a desired format for the document that they are expecting, including structure and data types. They will usually provide documentation that explains the format and provides examples.

Even when the most detailed, beautiful documentation is provided, it is not difficult to create errors in your data. To be clear, these aren’t syntax errors we are talking about here. These are errors of misunderstanding, like “I sent an apple, and you were expecting an orange.” In this book, I will refer to this type of validation as conformity validation so   that it may be distinguished from syntax validation.

In this scenario, the process usually plays out in the following steps:

1. You are finished creating your data and you feel confident.
2. You send your data across the Internet to the other party. Your Internet connection is slow today, and the data file you are sending is huge, so it takes several minutes.
3. You get an error response because your data was not formatted how they were expecting it. Confidence deflated. If you’re lucky, the error response will tell you something meaningful, like what ...