nodejs synchronous network request

In modern web development, we often need to make various network requests to obtain or send data. Common network requests include HTTP requests, WebSocket requests, and other third-party API requests, etc. In Node.js, we can use various npm packages to make network requests, such as axios, request, etc. These packages are all based on asynchronous IO to make network requests. However, in some special cases, we need to make synchronous network requests, that is, wait for the request to return the result before continuing to execute subsequent code. What should we do at this time?

This article will introduce a solution-using synchronous requests to make network requests. Synchronous requests have special advantages in certain scenarios. For example, in testing, data scraping, crawler and other scenarios, we need to wait for the request to return the result before proceeding with subsequent operations. At this time, using synchronous requests can simplify the code and improve the code efficiency. Readability and maintainability.

1. How to implement synchronous network requests

In Node.js, we can use Synchronous XHR or Sync XMLHttpRequest to implement synchronous network requests. Synchronous XHR is a native XMLHttpRequest object (XMLHttpRequest is a browser-side network request API that can make asynchronous and synchronous requests), while Sync XMLHttpRequest is a package implemented using Node.js EventEmitter and XMLHttpRequest.

In this article, we will use Sync XMLHttpRequest to implement synchronous network requests.

2. Use of Sync XMLHttpRequest

Before using Sync XMLHttpRequest, we need to install the npm package. It can be installed through the following command:

npm install sync-xmlhttprequest

After the installation is completed, we can use Sync XMLHttpRequest. The following is a simple usage example:

const SyncHttpRequest = require('sync-xmlhttprequest');
const url = 'https://jsonplaceholder.typicode.com/todos/1';

const req = new SyncHttpRequest();
const res = req.request('GET', url);

console.log(res.responseText);

In the above example, we call the request method in the instance req of SyncHttpRequest to make a GET request. This method accepts two parameters: request method and request address. After the request is sent, we can use res to obtain the response data, where the responseText attribute of res is the response data.

3. Precautions for using synchronous network requests in Node.js

When using synchronous network requests, you need to pay attention to the following points:

1. Synchronous network The request will block the event loop of Node.js. If the request response time is long, it will cause the Node.js application to be blocked, so synchronous network requests need to be used with caution.
2. When using Sync XMLHttpRequest, the require statement of the module needs to be placed at the top of the module, otherwise an error may occur.
3. When using synchronous network requests, if an error occurs in the request, an exception will be thrown directly instead of returned through the callback function.
4. In Node.js, synchronous network requests can only be executed in the main thread and cannot be executed in child threads.

4. Summary

Synchronous network requests have special advantages in certain scenarios, but you need to be aware that it may reduce the performance of Node.js applications and need to be used with caution. When using synchronous network requests, you can use the Sync XMLHttpRequest module to implement it. When using this module, you need to place its require statement at the top of the module, and be aware that an exception will be thrown directly when an error occurs.

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