How to convert JSON format data into JavaScript objects

JSON (JavaScript Object Notation) is JavaScript Object Notation, which is a lightweight data exchange format. JSON is stored and transmitted as text. It is easy to read, easy to maintain, and has good scalability. It is widely used in web applications.

In JavaScript, JSON format data can be converted into JavaScript objects to easily use the data. Here are several ways to convert JSON format into JavaScript objects.

Method 1: Use the JSON.parse() method
The JSON.parse() method can convert a JSON string into a JavaScript object. This method receives a string representing JSON as a parameter and returns a JavaScript object. The following is an example using the JSON.parse() method.

var jsonStr = '{"name":"Lucy","age":25,"gender":"female"}';
var jsonObj = JSON.parse(jsonStr);
console.log(jsonObj.name);        // 输出：Lucy
console.log(jsonObj.age);         // 输出：25
console.log(jsonObj.gender);      // 输出：female

Method 2: Use the eval() method
In some old browsers, the JSON.parse() method may not be supported. You can use the eval() method to convert the JSON string into a JavaScript object. . The eval() method will execute the incoming string as JavaScript code, so special attention needs to be paid to the security of the incoming string.

The following is an example of using the eval() method.

var jsonStr = '{"name":"Lucy","age":25,"gender":"female"}';
var jsonObj = eval('(' + jsonStr + ')');
console.log(jsonObj.name);        // 输出：Lucy
console.log(jsonObj.age);         // 输出：25
console.log(jsonObj.gender);      // 输出：female

It should be noted that when using the eval() method, the JSON string needs to be enclosed in parentheses, otherwise a syntax error will occur. In addition, the eval() method will execute the incoming string as JavaScript code, so you need to pay special attention to the security of the incoming string and do not use this method to process untrusted data.

Method 3: Use the Function() method
Similar to the eval() method, you can use the Function() method to convert a JSON string into a JavaScript object. The Function() method takes the passed in string as the function body, creates a new function, and executes the function immediately. You also need to pay special attention to the security of strings.

The following is an example of using the Function() method.

var jsonStr = '{"name":"Lucy","age":25,"gender":"female"}';
var jsonObj = (new Function('return ' + jsonStr))();
console.log(jsonObj.name);        // 输出：Lucy
console.log(jsonObj.age);         // 输出：25
console.log(jsonObj.gender);      // 输出：female

It should be noted that when using the Function() method, you need to concatenate the JSON string with "return" as the function body, otherwise a syntax error will occur. At the same time, special attention needs to be paid to the security of the incoming string.

Summary
The above introduces three methods of converting JSON format into JavaScript objects: JSON.parse() method, eval() method and Function() method. In actual use, it is recommended to use the JSON.parse() method for data conversion, because this method is safer and more efficient.

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