jquery/src/ajax/jsonp.js

(function( jQuery ) {

var jsc = jQuery.now(),
	jsre = /(\=)\?(&|$)|\?\?/i;

// Default jsonp settings
jQuery.ajaxSetup({
	jsonp: "callback",
	jsonpCallback: function() {
		return jQuery.expando + "_" + ( jsc++ );
	}
});

// Detect, normalize options and install callbacks for jsonp requests
jQuery.ajaxPrefilter( "json jsonp", function( s, originalSettings, jqXHR ) {

	var dataIsString = ( typeof s.data === "string" );

	if ( s.dataTypes[ 0 ] === "jsonp" ||
		originalSettings.jsonpCallback ||
		originalSettings.jsonp != null ||
		s.jsonp !== false && ( jsre.test( s.url ) ||
				dataIsString && jsre.test( s.data ) ) ) {

		var responseContainer,
			jsonpCallback = s.jsonpCallback =
				jQuery.isFunction( s.jsonpCallback ) ? s.jsonpCallback() : s.jsonpCallback,
			previous = window[ jsonpCallback ],
			url = s.url,
			data = s.data,
			replace = "$1" + jsonpCallback + "$2",
			cleanUp = function() {
				// Set callback back to previous value
				window[ jsonpCallback ] = previous;
				// Call if it was a function and we have a response
				if ( responseContainer && jQuery.isFunction( previous ) ) {
					window[ jsonpCallback ]( responseContainer[ 0 ] );
				}
			};

		if ( s.jsonp !== false ) {
			url = url.replace( jsre, replace );
			if ( s.url === url ) {
				if ( dataIsString ) {
					data = data.replace( jsre, replace );
				}
				if ( s.data === data ) {
					// Add callback manually
					url += (/\?/.test( url ) ? "&" : "?") + s.jsonp + "=" + jsonpCallback;
				}
			}
		}

		s.url = url;
		s.data = data;

		// Install callback
		window[ jsonpCallback ] = function( response ) {
			responseContainer = [ response ];
		};

		// Install cleanUp function
		jqXHR.then( cleanUp, cleanUp );

		// Use data converter to retrieve json after script execution
		s.converters["script json"] = function() {
			if ( !responseContainer ) {
				jQuery.error( jsonpCallback + " was not called" );
			}
			return responseContainer[ 0 ];
		};

		// force json dataType
		s.dataTypes[ 0 ] = "json";

		// Delegate to script
		return "script";
	}
} );

})( jQuery );