Let's say you have some code that takes some JSON as input, and then iterates over the elements of some array in that JSON. Since JSON is schemaless, you need t

Let's say you have some code that takes some JSON as input, and then iterates over the elements of some array in that JSON. Since JSON is schemaless, you need to check whether the array you want to iterate over is actually and array, and for each item you have to check if it has the correct type. Each time you access any data in the JSON you need to validate if it has the correct type, or you will end up with runtime errors. All that validation takes a lot of effort and makes your code hard to read. If you verify that the JSON input matches the expected schema at the very beginning, you can skip all the validation and error handling later, since you already know that is valid. This would make it a lot safer to handle external input. Then the next step would be if language & tooling also supported JSON schema, so that the way you access JSON documents in code also doesn't violate the schema. This would help prevent bugs from programmer errors.