d3.xhr = function(url, mimeType, callback) {

var xhr = {},

dispatch = d3.dispatch("progress", "load", "error"),

headers = {},

response = d3_identity,

request = new (window.XDomainRequest && /^(http(s)?:)?\/\//.test(url) ? XDomainRequest : XMLHttpRequest);

"onload" in request

? request.onload = request.onerror = respond

: request.onreadystatechange = function() { request.readyState > 3 && respond(); };

function respond() {

var s = request.status;

!s && request.responseText || s >= 200 && s < 300 || s === 304

? dispatch.load.call(xhr, response.call(xhr, request))

: dispatch.error.call(xhr, request);

}

request.onprogress = function(event) {

var o = d3.event;

d3.event = event;

try { dispatch.progress.call(xhr, request); }

finally { d3.event = o; }

};

xhr.header = function(name, value) {

name = (name + "").toLowerCase();

if (arguments.length < 2) return headers[name];

if (value == null) delete headers[name];

else headers[name] = value + "";

return xhr;

};

// If mimeType is non-null and no Accept header is set, a default is used.

xhr.mimeType = function(value) {

if (!arguments.length) return mimeType;

mimeType = value == null ? null : value + "";

return xhr;

};

// Specify how to convert the response content to a specific type;

// changes the callback value on "load" events.

xhr.response = function(value) {

response = value;

return xhr;

};

// Convenience methods.

["get", "post"].forEach(function(method) {

xhr[method] = function() {

return xhr.send.apply(xhr, [method].concat(d3_array(arguments)));

};

});

// If callback is non-null, it will be used for error and load events.

xhr.send = function(method, data, callback) {

if (arguments.length === 2 && typeof data === "function") callback = data, data = null;

request.open(method, url, true);

if (mimeType != null && !("accept" in headers)) headers["accept"] = mimeType + ",*/*";

if (request.setRequestHeader) for (var name in headers) request.setRequestHeader(name, headers[name]);

if (mimeType != null && request.overrideMimeType) request.overrideMimeType(mimeType);

if (callback != null) xhr.on("error", callback).on("load", function(request) { callback(null, request); });

request.send(data == null ? null : data);

return xhr;

};

xhr.abort = function() {

request.abort();

return xhr;

};

d3.rebind(xhr, dispatch, "on");

if (arguments.length === 2 && typeof mimeType === "function") callback = mimeType, mimeType = null;

return callback == null ? xhr : xhr.get(d3_xhr_fixCallback(callback));

};

function d3_xhr_fixCallback(callback) {

return callback.length === 1

? function(error, request) { callback(error == null ? request : null); }

: callback;

}