How to extract JSON from ajax

After obtaining JSON data with Ajax, you can extract it using the following methods:

1. Convert a JSON string into a JavaScript object.

var jsonData = JSON.parse(xhr.responseText);

The xhr.responseText represents the JSON string returned from the Ajax request.

1. Please rephrase the following sentence in English.
2. Can you please explain this concept?

var value = jsonData.propertyName; // 访问属性值

propertyName represents the property name in the JSON object.

1. In the case of

for (var key in jsonData) {
   var value = jsonData[key];
   // 对属性值进行操作
}

In this case, key represents the property name of the JSON object, and value represents the property value.

Please note that when using Ajax to retrieve JSON data, it is important to ensure that the returned data type is in JSON format. This can be done by specifying the Content-Type: application/json in the request header to ensure that the server returns JSON data.