What is json data

JSON data is a lightweight data exchange format that is based on a subset and uses a text format that is completely independent of programming languages ​​to store and represent data. Simplicity and clear hierarchical structure make JSON an ideal data exchange language.

JSONThe data is:

JSON (JavaScript Object Notation, JS object tag) It is a lightweight data exchange format. It is based on a subset of ECMAScript (the js specification developed by w3c) and uses a text format that is completely independent of programming languages ​​to store and represent data. Simplicity and clear hierarchical structure make JSON an ideal data exchange language. It is easy for people to read and write, and it is also easy for machines to parse and generate, and effectively improves network transmission efficiency. ——Baidu Encyclopedia

Data transmission is a scenario we often encounter when typing code, front-end and back-end interaction. Giving data a unified format helps us write and parse the data.

json is a data format that is widely used in data interaction with the backend.

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The birth of JSON

JSON is (JavaScript Object Notation, JS object markup), which is a data exchange format. Before the emergence of JSON, everyone had been using XML to transfer data. Because XML is a plain text format, it is suitable for exchanging data on the network. XML itself is not complicated, but with the addition of a lot of complex specifications such as DTD, XSD, XPath, and XSLT, any normal software developer will feel overwhelmed when encountering XML. In the end, everyone found that even if you study hard for Months later, I may not be able to figure out the XML specifications.

Finally, one day in 2002, in order to save software engineers who were in dire straits and had been fooled by several giant software companies for a long time, classmate Douglas Crockford invented the JSON super Lightweight data exchange format.

Because JSON is very simple, it quickly became popular in the Web world and became an ECMA standard. Almost all programming languages ​​have libraries for parsing JSON, and in JavaScript, we can use JSON directly because JavaScript has built-in JSON parsing. To turn any JavaScript object into JSON is to serialize the object into a JSON-formatted string so that it can be passed to other computers over the network. If we receive a string in JSON format, we only need to deserialize it into a JavaScript object, and we can use this object directly in JavaScript.

Escape

When we call the jsonp interface or call a js file, garbled characters may occur due to different file encodings. If your file contains non-English characters and the file encoding is inconsistent when calling, garbled characters will also appear.

This is why the data needs to be in a unified format.

• JSON is an efficient format for Ajax applications because it enables fast conversion between JavaScript objects and string values. JSON is a syntax for passing objects

• JSON is a built-in object that provides stringify and parse methods

• stringify converts js objects into strings that conform to json standards

• parse converts strings that conform to json standards into js objects

JSON has strict regulations on the type and format of values

• The value of the composite type can only be an array or object, not a function, regular expression object, or date object.

• There are only four simple types of values: string, numerical value (must be expressed in decimal), Boolean value and null (NaN, Infinity, -Infinity and undefined cannot be used).

• Strings must be expressed in double quotes, single quotes cannot be used.

• The key name of the object must be placed in double quotes.

• No comma can be added after the last member of an array or object.

PS: It should be noted that empty arrays and empty objects are both qualified JSON values, and null itself is also a qualified JSON value.

The syntax rules of JSON

The syntax rules of JSON are very simple, which can be called "elegant and perfect". To sum up, they are:

• Array is represented by square brackets ("[]").

• Object (Object) is represented by curly brackets ("{}").

• Name/value pairs (name/value) are combined into arrays and objects.

• The name (name) is placed in double quotes, and the value (value) includes string, numeric value, Boolean value, null, object and array.

• The parallel data are separated by commas (",")

Example

The writing format of JSON data is: name/value pairs.

The name in the name/value pair combination is written in front (in double quotes), and the value pair is written in the back, separated by colons,

Значение может быть: числом (целым или с плавающей запятой), строкой (в двойных кавычках), логическим значением (истина или ложь), массивом (в квадратных скобках), объектом (в фигурных скобках), нулем

varjson= {"password":123456,"name":"myname","Booleans":true,"Array":[x,y,z],"object":{}}

Или вложенное использование

Escape обзор

Зачем вам нужно escape? В js мы используем js-объекты для обработки, но при обмене данными с бэкендом мы отправляем строки в указанном формате json, поэтому при отправке или получении данных на бэкенд нам нужно экранировать

{name:"myname",password:123456}
"{"name":"myname","password":123456}"

Convert json string в объект js и вызовите метод синтаксического анализа:

• js object = JSON.parse(json string);

• js object в строку json, вызовите метод stringify:

• json string = JSON.stringify(js object);

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