JSON: a simple format that requires accurate structure

Useful to know

JSON is used to exchange data between programs and for files with ordered content. The format is textual and is historically related to the syntax of JavaScript, but is independent of a specific programming language. Its formal presentation begins with two main structures: a collection of name and value pairs and an orderly list of values. [1] This is enough for many practical tasks when participants in the exchange have a common understanding of what the individual fields should mean.

The object uses names for its properties, and the array arranges elements in a sequence. Values can include text, numbers, logical values , null and nested structures.[1] The difference is useful when modeling a catalog. An article can be an object with named parts, and the list of articles - an array. However, the form itself does not automatically determine which fields are required. It is a contract of the application that must be described and verified separately from the basic grammar of the form.

JSON has stricter rules than the usual JavaScript code. Property names are in double quotation marks, comments are not allowed, and the last comma after an element is invalid. Values such as undefined, NaN and Infinity do not belong to the standard JSON syntax. [2] Therefore, a fragment that seems convenient in a program file can be denied as an exchange file. Visual similarity is not reason enough for the two types of text to be processed as being completely the same.

In JavaScript, the JSON object provides conversion operations between text representation and program values. MDN describes the methods of reading and serializing as different directions of this process. [2] Successful reading proves that the text corresponds to the syntax; it does not prove that the value of each field is appropriate for the particular system. For example, a valid number may be unacceptable for a quantity, and a valid text may be too long for a title in the existing base.

Let's imagine an article import. The file may be an exact JSON and yet contain two identical addresses, an unknown category, or a missing title. These problems must be detected before recording the data. It is useful for the system to distinguish a read error from a content error and to indicate the specific field. Thus, the editor knows whether to fix a quote or change the value meaningfully instead of receiving a single general failure message.

With manual editing, it is a good habit to check the file after each substantial change and keep the previous working version. For larger sets, a preview without a record is useful, which shows what will be imported. JSON is convenient precisely because it is relatively simple and readable, but this simplicity does not negate the need for a contract for the data. A reliable exchange combines valid syntax, clear expectations of fields, and a predictable response to unacceptable content.