JSON headers is not working for array of objects

[Narixius]

Hi there.
I was working with this library and I found out in a special case, it doesn't add header content-type: application/json to the request.

What I did

$fetch("/api/endpoint", {method: "POST", body: [{num: 42}, {num: 43}]})

What I expected

Automatically add content-type: application/json header and stringify the body.

What actually happened

the content-type: application/json header was not added and the request body replaced with [object Object],[object Object]

Details

The request was not contain content-type: application/json header because as this feature implemented here, the toString() of the body in this case is not equal to [object Object] (actually it is equal to [object Object],[object Object] in this case). So automatic json headers and body stringify didn't happen.