Json abbreviation decoding. Basics of working with JSON. What is JSON

Variables, arrays and objects are a familiar and convenient form of data representation. It is customary to describe data in the browser language JavaScript, which is not necessary in the PHP server language. The JSON format allows you to summarize them into one whole and not focus on the programming language. In this case, the data turns into pairs: “name = value”. The value in each of them can also be a collection of such pairs.

It is customary to associate JSON with curly braces and the latter is quite justified, since the JSON format = JavaScript Object Notation. Much has changed in recent particularly dynamic years. What was created for a specific purpose often brought unexpected results or opened up new horizons.

AJAX technology has become traditional, regular page refresh entirely has ceased to be popular. A visitor, opening a site, initiates a series of partial data exchanges, when certain pages change only in the place that is relevant.

It is believed that the emergence of JSON is associated with the use of AJAX, but in fact, associative and its object notation (features of the syntax for describing and using objects) have a much more related relationship to JSON than the exchange of data between the browser and the server.

Since the content of the pages of modern sites has truly become “massive” (voluminous), the efficiency of the format for data exchange has acquired particular importance. This is not to say that JSON has become a new data representation, but the fact that it has long been an element of JavaScript syntax is significant.

The use of Cyrillic in naming variables is a very unexpected phenomenon (nonsense), but it works in the latest versions of Chrome, Firefox and even Internet Explorer 11.

Of course, there is no point in using this completely unexpected phenomenon, remembering how easily the values ​​of variables written in Russian letters turn into gibberish: what can we say about names, especially external ones.

It is doubtful that the initiative in Cyrillic names will be supported by the external environment of the browser, with which it constantly has to deal. But this fact deserves attention for the simple reason that the JSON format is the ability to write names and values ​​as the developer wishes. This is important, since in each task the description of the application area as it requires it significantly simplifies debugging and reduces the number of errors.

It doesn’t matter what exactly the basis of the syntactic innovation - JSON - was, it is important that it gave the legal right and the real opportunity to set the correspondence: “any name = any value”.

We must pay tribute to the JavaScript language: what is provided by the syntax does not oblige the developer and does not impose anything on him. The developer freely uses the language syntax to optimally form a data model and an algorithm for their use.

By accepting data in JSON format, the server (via PHP, in particular) provides the ability to process it as is and return the result back to the browser in a similar format. PHP source array:

• $cJSON = array ("a"=> "alfa", "b"=> "beta", "g"=> "gamma").

Convert to JSON for delivery to browser:

• $cJS = json_encode($cJSON).

Result:

• ("a":"alfa","b":"beta","g":"gamma").

The nesting shown in the photo is allowed.

Here the generated array was added with a new element “into itself” with the automatic index “0”, and then again with the specified index “z”.

Json_decode() converts a JSON string to a PHP array. Similar results can be achieved by manipulating functions and explode(). In some cases this option is preferable.

Elements can be nested both on the browser side and on the server side. In practice, the JSON format (RFC 4627 standard description) provides significantly more than 4 levels of nesting, but this feature should not be abused.

It is best to never go beyond reasonable sufficiency; this makes the code readable, making it easier to debug and understand for other developers.

JSON is commonly referred to as data constructs that are simpler than XML and understandable to both people and computers. This is true when the amount of data is small and the developer has chosen the level of nesting wisely. In all other cases, counting the number of brackets and understanding is difficult both on the browser side and on the server side.

The use of JSON in practice is often not limited to a human-readable short string. Any data construction is always pragmatic. At the same time, JSON can be effectively used both in real task data (enterprise staff) and for implementing temporary data (object cache).

Usually a record about one person is a last name, first name, patronymic, year of birth, specialty, education, ... and a few other simple values. Even in particularly demanding companies, a record about one person will not exceed a dozen or two fields. This is perceptible and can be placed in a database string.

If a company employs several people, this is one thing, but if there are tens of thousands, this is completely different. You can continue to use the database, but storing it as a file seems more practical and accessible to use.

JSON is a plain text file. The case with the staffing table goes without saying. You can always read it. Opening and editing is also available in any text editor that does not have the habit of adding its own service information to the contents of the file. In general, *.json is pure text both inside the browser and inside the file - a string.

The photo shows the cache of the object that forms the picture, an example.

This is an example of the content of a file generated by a site that provides color 3D printing on mugs and ceramics. Naturally, having such a JSON format, deciding how to open it is really problematic. However, in this and similar cases there are no problems with reading the file: PHP reads the file, parses it and passes it to the browser. The data changed by the visitor is returned to the server and written back.

In this use case, the file acts as a variable that is stored outside of the code. If necessary, the variable receives a value from the file, and if it is changed by the visitor in the dialogue provided by the site, then all changes will be recorded as is. There is no need to read and check the contents of the file.

JSON is often used to store and use service information - this is not a staffing table, and neither the developer nor the site visitor needs to see it.

“There is a time for everything” is a classical knowledge accepted as an axiom even before the advent of programming. “Nothing just appears” - this also happened before man wrote the first intelligible program in an artificial language.

Data formats arise from real needs and are based on achieved knowledge. HTML has its own path, XML has its own path, and JSON is JavaScript object logic extended to other languages. Comparing one with another is not the best thing to do. To each his own.

XML copes with its tasks wonderfully and is clearly not going to become history. And JSON was used until 2006; it’s just that not every developer considered it his duty to declare certain options for representing their data.

There have been cases in practice when programs were written in BASIC that did not use JSON as such, but perfectly stored “name = value” pairs and made them available to the right algorithms at the right time.

The habit of working with associative arrays and objects in JavaScript makes using JSON natural and convenient. This is a really great format, but the ability to separate and join, manipulating strings and arrays, has much deeper roots.

The join/split functions of the JavaScript language and implode/explode of the PHP language allow you to conveniently and efficiently use both XML, JSON data formats, and your own version. The latter is often optimal, while the first two are ideal for general use options. If information is being transferred to another developer, server, file or database, there is no better way to find XML and JSON. Everyone works with them, so the transmission/reception of information does not require comments.

Reading and writing data in JSON format in Android is not only the norm, but there are also many objects focused on working with this particular data format.

In this case, the JSON format is used. This may be true, but the question is not the phenomenality of social networks, but the fact that presenting information in the “name = value” format is really convenient both for programming and for use. Unlike the strict and complex “XML”, this is truly a human-friendly format.

It so happens that variables must be described (JavaScript) or at least an initial value must be specified (PHP). In both cases, the variable can change its type very easily. The language performs this conversion automatically if necessary.

But why shouldn’t the variable also change its name, appear during the execution of the algorithm, and disappear when it is no longer needed? Associative arrays solve this problem, but then when using such relatively dynamic variables, the array name and the corresponding syntactic constructs will follow where they are used.

This circumstance is especially pronounced in PHP, but you can put up with it, as, indeed, with the “$” symbol in the variable name and the “$this->” combination inside the object. Programming in JavaScript and PHP at the same time, at first you really are amazed at how different everything is, but then everything becomes so familiar and natural...

In this example, a *.docx document is created using the PHPOffice/PHPWord library, and the aProperties array contains the properties of this document (author, company, title, category, creation date...).

The second array contains data for the page:

• orientation (landscape or normal);
• vertical and horizontal dimensions;
• indents (margins left, top, bottom, right);
• headers and footers.

The document is generated on the server where the PHPOffice/PHPWord library is installed. The site allows you to manage the values ​​of these arrays using JavaScript. The result in JSON format is returned back to the server and used in PHP algorithms, in its constructs, that is, in arrays.

The JSON format solves the problem of dynamic variables. Here you can create, change and delete variables without unnecessary syntactic clutter. It looks nice and is used in JavaScript.

In this example, the GetOjInfo() function retrieves the value name and value from an object. Initially, the JSON string object assigned to the ojInfo variable has three elements: Name, age, and work. A little later the Status variable is added.

After the first delete operator, the ojInfo line loses the age element, after the second delete it loses the work element. If we assume that this string is a selection of variables that have a certain meaning, then using JSON you can actually create, change and delete any sets of them outside the operational field (syntax) of describing and processing the JavaScript language.

The JSON format was not designed for this option, but it is possible, practical and convenient.

JSON (JavaScript Object Notation) is a data transfer format. As the name suggests, the format is based on the JavaScript programming language, but it is also available in other languages ​​(Python, Ruby, PHP, Java).

JSON uses the .json extension. When used in other file formats (such as .html), the JSON string is quoted or assigned to a variable. This format is easily transferred between the web server and the client or browser.

Lightweight and easy to understand, JSON is a great alternative to XML.

This tutorial will introduce you to the benefits, objects, general structure, and syntax of JSON.

A JSON object is in key-value form and is usually written in curly braces. When working with JSON, all objects are stored in a .json file, but they can also exist as separate objects in the context of the program.

The JSON object looks like this:

"first_name" : "John",
"last_name" : "Smith",
"location" : "London",
"online" : true,
"followers" : 987

This is a very simple example. A JSON object can contain many lines.

As you can see, an object is made up of key-value pairs that are enclosed in curly braces. Most data in JSON is written as objects.

A colon is placed between the key and value. After each pair you need to put a comma. The result is:

"key" : "value", "key" : "value", "key" : "value"

The JSON key is on the left. The key must be placed in double quotes. Any valid string can be used as a key. Within one object, all keys must be unique. The key may contain a space (“first name”), but programming may have problems accessing such a key. Therefore, instead of a space, it is better to use an underscore (“first_name”).

The JSON values ​​are on the right side of the column. Any simple data type can be used as a value:

• Strings
• Numbers
• Objects
• Arrays
• Boolean data (true or false)

Values ​​can also be represented by complex data types (for example, objects or JSON arrays).

JSON supports individual syntax for each of the data types listed above: if the value is represented by a string, then it will be quoted, but if it is a number, then it will not.

Typically, data in .json files is written in a column, but JSON can also be written in a row:

( "first_name" : "John", "last_name" : "Smith", "online" : true, )

This is how JSON data is typically written to other file types.

By writing JSON data to a column, you improve the readability of the file (especially if there is a lot of data in the file). JSON ignores spaces between columns, so you can use them to divide your data into a manageable number of columns.

"first_name" : "John",
"last_name" : "Smith",
"online" : true

Note that JSON objects are very similar to JavaScript objects, but they are not the same format. For example, you can use functions in JavaScript, but not in JSON.

The main advantage of JSON is that data in this format is supported by many popular programming languages, so it can be quickly transferred.

You are now familiar with the basic JSON syntax. But JSON files can have complex, hierarchical structures that include nested arrays and objects.

JSON can store nested objects and arrays, which will be passed as the value of the key assigned to them.

Below you will find an example - the users.json file, which contains user data. For each user

(“john”, “jesse”, “drew”, “jamie”) a nested object is passed as a value, which, in turn, also consists of keys and values.

Note: The first nested JSON object is highlighted in red.

"john" :(
"username" : "John",
"location" : "London",
"online" : true,
"followers" : 987

"jesse" :(
"username" : "Jesse",
"location" : "Washington",
"online" : false,
"followers" : 432

"drew" :(
"username" : "Drew",
"location" : "Paris",
"online" : false,
"followers" : 321

"jamie" :(
"username" : "Jamie",
"location" : "Berlin",
"online" : true,
"followers" : 654

Note that curly braces are used in both the nested object and the main object. Commas in nested objects are used in the same way as in regular objects.

Data can be nested in JSON using JavaScript arrays, which will be passed as values. JavaScript uses square brackets () at the beginning and end of an array. An array is an ordered collection of data that can contain different types of data.

An array is used to transfer a large amount of data that can be grouped. For example, let's try to record user data.

{
"first_name" : "John",
"last_name" : "Smith",
"location" : "London",
"websites" : [

"description" : "work",
"URL" : "https://www.johnsmithsite.com/"

},
{

"desciption" : "tutorials",
"URL" : "https://www.johnsmithsite.com/tutorials"

"social_media" : [

"description" : "twitter",
"link" : "https://twitter.com/johnsmith"

"description" : "facebook",
"link" : "https://www.facebook.com/johnsmith"

"description" : "github",
"link" : "https://github.com/johnsmith"

The keys “websites” and “social_media” are assigned arrays as values, which are placed in square brackets.

Using nested arrays and objects, you can create a complex data hierarchy.

XML (eXtensible Markup Language) allows you to store data in a form that is easy to understand for humans and machines. The XML format is supported by a large number of programming languages.

XML and JSON have a lot in common. However, XML requires much more text, which means that such files are larger and more difficult to read and write. Moreover, XML is only processed using an XML interpreter, while JSON can be processed using a simple function. Unlike JSON, XML cannot store arrays.

Let's compare two files: they contain the same data, but the first is written in XML format, and the second in JSON.

users.xml

John London

Jesse Washington

Drew Paris

Jamie Berlin

users.json
("users": [

("username" : "John", "location" : "London"),
("username" : "Jesse", "location" : "Washington"),
("username" : "Drew", "location" : "Paris"),
("username" : "JamieMantisShrimp", "location" : "Berlin")

JSON is a very compact format and does not require as many tags as XML. Additionally, XML, unlike JSON, does not support arrays.

If you're familiar with HTML, you'll notice that the XML format is very similar to it (particularly the tags). JSON is simpler, requires less text, and is easier to use in AJAX applications, for example.

Of course, the format must be chosen depending on the needs of the application.

JSON is commonly used in JavaScript, but the format is widely used in other programming languages.

More information about JSON compatibility and processing can be found on the project website and the jQuery library.

It's rare to write JSON from scratch. Typically, data is loaded from source or converted to JSON. You can convert CSV or tab-delimited data to JSON using the open-source tool Mr. Data Converter. To convert XML to JSON and vice versa, use utilities-online.info. When working with automatic tools, be sure to check the results.

JSON files (including converted data) can be inspected using the JSONLint service. To test JSON in a web development context, refer to JSFiddle.

JSON is a simple and lightweight data format. JSON files are easy to transfer, store, and use.

Today JSON is often used in APIs.

JavaScript Object Notation (JSON) is a standard text format for representing structured data based on JavaScript object syntax. It is commonly used for data transfer in web applications (for example, sending some data from the server to the client so it can be displayed on a web page or vice versa). You'll run into this quite often, so in this article we give you everything you need to work with JSON using JavaScript, including parsing JSON so you can access the data inside it and create JSON.

We're going to load it into our page and use some neat DOM manipulation to render it, like this:

To receive the JSON, we'll use an API called XMLHttpRequest (often called XHR). This is a very useful JavaScript object that allows us to make network requests to retrieve resources from the server via JavaScript (e.g. images, text, JSON, even HTML snippets), meaning we can update small sections of content without having to reload the entire page. This has resulted in more responsive web pages and sounds exciting, but is unfortunately beyond the scope of this article to teach it in much more detail.

Here we store the response to our request (available in the property) in the superHeroes variable; this variable will now contain a JSON based JavaScript object! We then pass this object to two function calls - the first one will populate it with the correct data, and the second one will create an info card for each hero on the team and insert it into .

We wrapped the code in an event handler that fires when the load event is fired on the request object (see) - this is because the load event fires when the response is returned successfully; doing it this way ensures that request.response will definitely be available when we go to try and do something about it.

Now we have extracted the JSON data and turned it into a JavaScript object, let's make use of it by writing the two functions we have linked above. First of all, add the following function definition below the previous code:

Function populateHeader(jsonObj) ( var myH1 = document.createElement("h1"); myH1.textContent = jsonObj["squadName"]; header.appendChild(myH1); var myPara = document.createElement("p"); myPara. textContent = "Hometown: " + jsonObj["homeTown"] + " // Formed: " + jsonObj["formed"]; header.appendChild(myPara);

We named the parameter jsonObj to remind ourselves that this JavaScript object originated from JSON. Here we first create an element with , set it equal to the squadName property of the object, and then add it to the header with . We then perform a very similar operation with a paragraph: we create it, set its text content, and add it to the heading. The only difference is that its text is specified as a concatenated string containing both the homeTown and formed properties of the object.

Then add the following function at the bottom of the code that creates and displays the superhero cards:

Function showHeroes(jsonObj) ( var heroes = jsonObj["members"]; for (var i = 0; i< heroes.length; i++) { var myArticle = document.createElement("article"); var myH2 = document.createElement("h2"); var myPara1 = document.createElement("p"); var myPara2 = document.createElement("p"); var myPara3 = document.createElement("p"); var myList = document.createElement("ul"); myH2.textContent = heroes[i].name; myPara1.textContent = "Secret identity: " + heroes[i].secretIdentity; myPara2.textContent = "Age: " + heroes[i].age; myPara3.textContent = "Superpowers:"; var superPowers = heroes[i].powers; for (var j = 0; j < superPowers.length; j++) { var listItem = document.createElement("li"); listItem.textContent = superPowers[j]; myList.appendChild(listItem); } myArticle.appendChild(myH2); myArticle.appendChild(myPara1); myArticle.appendChild(myPara2); myArticle.appendChild(myPara3); myArticle.appendChild(myList); section.appendChild(myArticle); } }

First, let's store the members property of the JavaScript object in a new variable. This array contains several objects that contain information for each hero.

We then use to loop through each object in the array. For each of them we: