It may be that you face issues while working with web services and APIs, where identifying their causes can be challenging. In the web world, HTTP headers are one of the tools that help us transfer important information and identify problems. The NEL (Network Error Logging) header is also one of these tools that can assist developers in tracking and reporting network errors in more detail.
The NEL header allows for recording and reporting network errors, aiming to provide information that is more precise regarding errors occurring from the user to the server. This header can help developers better understand complex issues and take necessary actions to improve user experience.
NEL Header Structure
The NEL header utilizes a JSON structure that includes more detailed information about how and when to log errors. In this structure, you can specify which errors should be reported and where they should be sent.
An example of the code structure for the amount and use of the NEL header is as follows:
fetch('https://api.example.com/data', {
method: 'GET',
headers: {
'Content-Type': 'application/json',
'NEL': '{ "report_to": "endpoint", "max_age": 2592000, "failure_fraction": 1.0 }'
}
});
Explanation of Code Line by Line
fetch('https://api.example.com/data', {
In this line, the fetch function is used to send a GET request to the specified URL.
method: 'GET',
This option indicates that the HTTP request type is GET.
headers: {
In this section, the HTTP headers are specified.
'Content-Type': 'application/json',
This specifies the content type of the request, which is JSON here.
'NEL': '{ "report_to": "endpoint", "max_age": 2592000, "failure_fraction": 1.0 }'
This specifies the NEL header, which contains parameters for reporting errors, including the endpoint address, the time duration for which the validity lasts, and the failure rate.
}
This marks the end of the headers section.
});
This marks the end of the fetch function.