$http data vs params when making POST request - angularjs

Question

Preface: I am using AngularJS 1.5.9.
When writing my service, this code works when posting to the server:
var request = {
url: '/connect/token',
method: 'POST',
data: $httpParamSerializer(params),
headers: {
'Content-Type': 'application/x-www-form-urlencoded'
}
};
$http(request).then(function(response) {});
However, it seems counterintuitive to use data when $http has the usage argument params, with the following definition as per AngularJS's documentation:
params – {Object.} – Map of strings or objects which
will be serialized with the paramSerializer and appended as GET
parameters.
As you can see, the documentation specifies that this argument is meant to be used only for GET requests. I confirmed as much when I attempted to use the params argument with my POST request:
var request = {
url: '/connect/token',
method: 'POST',
params: params,
headers: {
'Content-Type': 'application/x-www-form-urlencoded'
}
};
$http(request).then(function(response) {});
When you submit the POST request in this way, you get the following response from the server:
{
"error":"invalid_request",
"error_description":"A malformed token request has been received: the mandatory 'Content-Type' header was missing from the POST request."
}
In other words, if I don't use the data argument and invoke the param serializer service on the params I want to pass in, my custom service won't set the Content-Type header on my request, I've confirmed this in the network tab of the web inspector.
TLDR; Why do I have to use the data argument and serialize the params instead of just using the params argument directly? And why is the content type I specify ignored when I do use the params argument?

Answer 1

Use params option for GET requests.
With params option you can set URL query string parameters like baseurl.com?myParam=something