How to make navigator.sendBeacon use GET method

Question

I want to use navigator.sendBeacon in a client's website. But it is using the POST method and the request is not reaching the server as the request url's domain is different. I tried different ways of using sendBeacon(), but all are using the POST method.

1.

var data = new FormData();<br>
navigator.sendBeacon(myurl, data);

2. navigator.sendBeacon(myurl, "");

3. navigator.sendBeacon(myurl);

Is there a way to make GET call using sendBeacon()? Or is there any way to use sendBeacon() in a cross-domain environment.

Answer 1

From the W3C specification, on which browser implementations are based:

The sendBeacon() method does not provide ability to customize the request method. Applications that require non-default settings for such requests should use the FETCH API with keep-alive flag set to true.

Per this documentation, here's an example of how the Fetch API can be used to replicate the behavior of sendBeacon:

fetch(url, {
  method: ..., 
  body: ...,            
  headers: ...,       
  credentials: 'include',
  mode: 'no-cors',
  keep-alive: true,
})

Answer 2

Although navigator.sendBeacon uses POST you can still pass the data as a ?query=string and this will reach the URL endpoint.

You can then simply parse the URL on the server and extract the data that way.

I use this for approach to debug production sites when I want to keep the DevTools closed but still see messages in my local terminal. Here is the output...

navigator.sendBeacon("http://127.0.0.1:8000/?"+string, string);

127.0.0.1 - - [28/Jan/2021 21:26:43] code 501, message Unsupported method ('POST')
127.0.0.1 - - [28/Jan/2021 21:26:43] "POST /?window-hidden HTTP/1.1" 501 -
127.0.0.1 - - [28/Jan/2021 21:27:42] code 501, message Unsupported method ('POST')
127.0.0.1 - - [28/Jan/2021 21:27:42] "POST /?window%20focus HTTP/1.1" 501 -
127.0.0.1 - - [28/Jan/2021 21:27:42] code 501, message Unsupported method ('POST')
127.0.0.1 - - [28/Jan/2021 21:27:42] "POST /?window%20blur HTTP/1.1" 501 -
127.0.0.1 - - [28/Jan/2021 21:27:42] code 501, message Unsupported method ('POST')
127.0.0.1 - - [28/Jan/2021 21:27:42] "POST /?window%20-%20hidden HTTP/1.1" 501 -