When dataType is set to "auto", the response Content-Type header will be used to determine the type of data received (xml, html, script, json, text). If the header is javascript or json, the data will be evaluated/parsed.

This allows multiple expected dataTypes.

httpData: function( xhr, type, s ) {
	var ct = xhr.getResponseHeader("content-type"),
		xml = type === "xml" || (!type || type === "auto") && ct && ct.indexOf("xml") >= 0,
		data = xml ? xhr.responseXML : xhr.responseText;

	if ( xml && data.documentElement.nodeName === "parsererror" ) {
		throw "parsererror";
	}

	// Allow a pre-filtering function to sanitize the response
	// s is checked to keep backwards compatibility
	if ( s && s.dataFilter ) {
		data = s.dataFilter( data, type );
	}

	// The filter can actually parse the response
	if ( typeof data === "string" ) {

		// If the type is "script", eval it in global context
		if ( type === "script" || (type === "auto" && ct && ct.indexOf("javascript") >= 0) ) {
			jQuery.globalEval( data );
		}

		// Get the JavaScript object, if JSON is used.
		if ( type === "json" || (type === "auto" && ct && ct.indexOf("json") >= 0) ) {
			if ( typeof JSON === "object" && JSON.parse ) {
				data = JSON.parse( data );
			} else {
				data = (new Function("return " + data))();
			}
		}
	}

	return data;
}