nodejs request returns json data

Node.js is a very popular server-side JavaScript runtime environment. It is a powerful tool for building high-performance web applications. HTTP requests are essential when you need to collect data from an API function. Because most modern APIs return data in JSON format, handling how to request and return JSON data is a very important task in Node.js.

In Node.js, we can use the built-in http module to make HTTP requests. You can get data from the remote server by sending an HTTP request and parse it into JSON format data. The following is an example of making an HTTP request and receiving a JSON response using Node.js:

const https = require('https');

const options = {
    hostname: 'api.example.com',
    port: 443,
    path: '/data',
    method: 'GET'
};

const req = https.request(options, res => {
    console.log(`statusCode: ${res.statusCode}`);

    let data = '';

    res.on('data', d => {
        data += d;
    });

    res.on('end', () => {
        const json = JSON.parse(data);
        console.log(json);
    });
});

req.on('error', error => {
    console.error(error);
});

req.end();

In the above example, the https module provides a request() Function in which we pass an options object as a parameter. This object contains information such as hostname, port, request path and request method. The request() function returns a http.ClientRequest object, and we can call the end() method of the object to send the request.

When the remote server responds to the request, we can listen to the "data" event of the response and add the data to the buffer. When the response is completed, we can use the JSON.parse() function to parse the data in the buffer into JSON format data.

When processing API responses, we need to ensure that the status code of the HTTP response is 200. But this is not the only status code that needs to be handled, there are other common status codes:

• 404 (Not Found): The requested resource does not exist
• 401 (Unauthorized): The user is required to provide legal identity certificate
• 500 (Internal Server Error): The server encountered an unpredictable error

We also need to handle these status codes. For example, when a request returns a 404 response code, we can send a message like "Resource Not Found" to the user.

const https = require('https');

const options = {
    hostname: 'api.example.com',
    port: 443,
    path: '/data',
    method: 'GET'
};

const req = https.request(options, res => {
    let data = '';

    res.on('data', d => {
        data += d;
    });

    res.on('end', () => {
        const json = JSON.parse(data);
        console.log(json);
    });
});

req.on('error', error => {
    console.error(error);
});

req.end();

In the above example, we ignored the HTTP response status code. While this is convenient, it is very unsafe. If the server returns an error status code, we may need to know the cause of the error. In order to achieve this goal, we need to check the response status code in the callback of the request() function. If the status code is not 200, we can use the res.statusMessage field to get the response status message:

const https = require('https');

const options = {
    hostname: 'api.example.com',
    port: 443,
    path: '/data',
    method: 'GET'
};

const req = https.request(options, res => {
    if (res.statusCode !== 200) {
        console.error(`请求失败： ${res.statusMessage}`);
        res.resume();
        return;
    }

    let data = '';

    res.on('data', d => {
        data += d;
    });

    res.on('end', () => {
        const json = JSON.parse(data);
        console.log(json);
    });
});

req.on('error', error => {
    console.error(error);
});

req.end();

In the above code, we print out the error message when the HTTP response status code is not 200 . If an error is encountered, we call the res.resume() method to clear the cache and end the response when the data is processed. If you encounter a request error that is not caused by your code, it is sometimes useful to call the res.resume() method.

Summary

Requesting and parsing JSON data in Node.js is very easy. The built-in HTTP module provides a request function. By using this function, we can send HTTP requests and receive Json responses in Node.js programs. Using the above code, we can get the API endpoint data and easily parse the JSON format data. However, we need to pay attention to some abnormal situations, such as HTTP response status code is not 200, and other HTTP request errors. With complete error handling we can make our code more robust.

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