Get XMLHttpRequest REST response in json format

Question

I'm trying to do a REST call to get current user information without using jQuery to handle the ajax. I've got this code:

var xmlhttp = new XMLHttpRequest();

xmlhttp.onreadystatechange = function(){
    if(xmlhttp.readyState == XMLHttpRequest.DONE){
        if(xmlhttp.status == 200){
            console.log(JSON.parse(xmlhttp.responseText))
        } else if (xmlhttp.status == 400){
            console.log("not found")
        } else {
            console.log("other")
        }
    }
}
xmlhttp.responseType="json"
xmlhttp.open("GET","https://,site/_api/web/currentuser?$format=json",true);
xmlhttp.send()

This works, but the response comes back as xml not json. Is there a way to tell the SP to return json when using XHR?

I tried the $format=json parameter, but that evidently isn't supported by the SP 2013 REST api. Nor is XMLHttpRequest.responseType supported by browsers.

Answer 1

You have to set the Accept request header to application/json; odata=verbose using XMLHttpRequest.setRequestHeader().

SharePoint looks at this header to decide if the data has to be sent as JSON or XML.