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Will the ‘error’ event ever be emitted on ‘http.IncomingMessage’ in a node.js http.request ?

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In this article, we will see how to handle the ‘error’ event that is emitted on ‘http.IncomingMessage’ in a node.js http.request.

In Node.js, the ‘http.IncomingMessage‘ object is used to represent the incoming HTTP request message. This object is a readable stream, and it can emit various events such as ‘data’, ‘end’, and ‘error’. One of the events that can be emitted by this object is the ‘error’ event, which is triggered when an error occurs while processing the incoming request.

The problem is that in some cases, the ‘error’ event is not emitted when an error occurs during an HTTP request. This can be a problem because, without the ‘error’ event, it is difficult to detect and handle errors that occur during the request.

Example: Here is an example of a problem that can occur when the ‘error’ event is not emitted.

Javascript




const http=require('http');
 
const req=http.request({
    host:nonexistent-host.com,
    path:'/',
    method:'GET'
},res=>{
    console.log('status code:',res.statusCode);
});
 
res.end();


Output: In this example, we are making a GET request to a non-existent host. The expected output is an error event, but the actual output is nothing.

 

Solution: To solve this error, we have the following solution

The solution to this problem is to add a listener for the ‘error’ event on the ‘http.IncomingMessage’ object. This way, if an error occurs during the request, it will be caught and handled by the listener.

Example: Here is an example of how to add a listener for the ‘error’ event.

Javascript




const http=require('http');
 
const req=http.request({
     
    // The non-exist host
    host:'nonexistent-host.com',                   
    path:'/',
    method:'GET'
},res=>{
     
    // Consoling the status code
    console.log('status code:',res.statusCode);       
});
 
 
// Solution
req.on('error',err=>{
     
    // Catching the error and printing the message
    console.error(`request error:${err.message}`);       
});
req.end();


Output: In this example, we added a listener for the ‘error’ event on the ‘req’ object, which is an instance of the ‘http.IncomingMessage’ object. Now, if an error occurs during the request, the listener will catch it and print an error message to the console.

request error:getaddrinfo ENOTFOUND nonexistent-host.com

In conclusion, the ‘error’ event is an important feature of the ‘http.IncomingMessage’ object in Node.js, as it allows developers to detect and handle errors that occur during an HTTP request. However, in some cases, the ‘error’ event is not emitted when an error occurs. To solve this problem, developers should add a listener for the ‘error’ event on the ‘http.IncomingMessage’ object. This way, any errors that occur during the request will be caught and handled, ensuring a smooth and reliable user experience.



Last Updated : 31 Jan, 2023
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