Javascript API POST Request from URL

Question

Forgive me if I have titled this tread wrong, I don't know the correct terminology.

I have a link with values included, they are: id and environment therefore the url it formatted such ad https://foo.com?id=1234&e=s

With this url I need to take the id and the environment (Stage or production) and create a post body to set a flag as true.

So if e=s (environment = stage) I need post to
https://services-stage.foo.com/api/account//flag

Or if e = p (production) https://services.foo.com/api/account//flag

Where = the id in the url

With POST body:

        {
    "type": OptionFlag,   
    "flag": true   //Flag should be set to true
        }

My problem is I don't know where to start with my limited javascript knowledge. I have created GET requests form api's in the past but never POST and never with parameters in the URL.

I now understand how to handle the post, however I am still at a loss on how I would get the Id and the environment data from the url to then pass them to the ajax url in the function.

function CustomerId(){
    //Function for getting id number from URL
}

function apiEnvironment(){
     //Function for getting environment from URL

}

function OptOut(CustomerId, apiEnvironment) {
        jQuery.ajax({
            type: 'POST',
            url: apiEnvironment + '/api/v1/account/' + CustomerId + '/optOut',
            dataType: 'json',
            contentType: 'application/json; charset=UTF-8',
            data : data,
            success: {
            }
        });
    }

This Is what I have so far...