MySql and Javascript: How to process JSON data

With the continuous development of Internet technology, data in JSON (JavaScript Object Notation) format is becoming more and more common. In web applications, it is often necessary to store JSON data in a database, and then use Javascript to extract the data from the database and display it on the web page. However, how to handle this JSON data, especially in MySQL and Javascript, is often confusing.

This article will introduce readers to how to process JSON data, including using MySQL to store JSON data and using Javascript to query, update and display JSON data.

JSON data processing in MySQL

MySQL supports the JSON data type starting from version 5.7.8, which provides a very convenient way to process JSON data. Like other data types, the JSON data type can be used to define table structures. Here is an example:

CREATE TABLE products (
  id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(100) NOT NULL,
  price FLOAT(10,2) NOT NULL,
  category_id INT UNSIGNED NOT NULL,
  details JSON
);

As you can see, this table has a column of JSON data type named details, which is used to store product details. Since the JSON data type supports indexing, JSON columns can be retrieved and sorted. In practical applications, the table structure for storing JSON data can be adjusted as needed.

In MySQL, you can use the JSON_OBJECT() function to convert data to JSON format, and use the JSON_EXTRACT() function to query JSON data. For example, the following is some sample code:

-- 插入 JSON 数据
INSERT INTO products (name, price, category_id, details)
VALUES ('iPhone', 999, 1, 
        JSON_OBJECT('color', 'black',
                    'capacity', '256 GB',
                    'features', JSON_ARRAY('wireless charging', 'face recognition')));

-- 查询 JSON 数据
SELECT * FROM products WHERE JSON_EXTRACT(details, '$.color') = 'black';

-- 更新 JSON 数据
UPDATE products SET details = JSON_SET(details, '$.capacity', '512 GB') WHERE id = 1;

-- 删除 JSON 数据
DELETE FROM products WHERE JSON_EXTRACT(details, '$.features[1]') = 'face recognition';

In MySQL, you can use JSON type-specific operations to perform data operations such as adding, deleting, modifying, and querying JSON data. For more JSON operations, you can check the MySQL official documentation.

JSON data processing in Javascript

JSON data processing in Javascript is more common than MySQL. How to parse JSON into Javascript objects and how to convert Javascript objects into JSON format strings are the most basic JSON processing methods in Javascript.

For example, here is how to parse a Javascript object from a JSON string:

const jsonString = '{"name":"andy","age":20}';
const jsonObject = JSON.parse(jsonString);
console.log(jsonObject.name); // 输出 andy
console.log(jsonObject.age);  // 输出 20

The way to manipulate any Javascript object and convert it into a JSON format string is as follows:

const product = {
  name: 'iPhone',
  price: 999,
  category_id: 1,
  details: {
    color: 'black',
    capacity: '256 GB',
    features: ['wireless charging', 'face recognition']
  }
};
const jsonString = JSON.stringify(product);
console.log(jsonString); // 输出 {"name":"iPhone","price":999,"category_id":1,"details":{"color":"black","capacity":"256 GB","features":["wireless charging","face recognition"]}}

This JSON format string can be passed to the server for query, or displayed to the user in the front-end interface.

In addition, common Javascript libraries (such as jQuery, React, etc.) also provide many functions and methods to process JSON data. For example, the code that uses jQuery to send a POST request to the server and receive JSON data is as follows:

const data = { name: 'andy', age: 20 };
$.post('/api', data, function(response) {
  console.log(response);
}, 'json');

The above code will send a POST request to the server address '/api' and pass the Javascript object data through the POST request to server. The received server response is a Javascript object that can be parsed and used in JSON format.

Conclusion

Processing JSON data is one of the very common operations in web applications. This article mainly introduces methods of processing JSON data in MySQL and JavaScript. MySQL can use the JSON data type to store and operate JSON data, while Javascript uses built-in JSON objects and third-party libraries to parse, modify, and display JSON data.

Mastering the basic skills of processing JSON data can make web applications more efficient and flexible in processing data, and have a better user experience.

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