jsonp.js

/*
 * Copyright 2012-2014 the original author or authors
 * @license MIT, see LICENSE.txt for details
 *
 * @author Scott Andrews
 */

(function (define, global, document) {
	'use strict';

	var undef;

	define(function (require) {

		var when, UrlBuilder, responsePromise, client;

		when = require('when');
		UrlBuilder = require('../UrlBuilder');
		responsePromise = require('../util/responsePromise');
		client = require('../client');

		// consider abstracting this into a util module
		function clearProperty(scope, propertyName) {
			try {
				delete scope[propertyName];
			}
			catch (e) {
				// IE doesn't like to delete properties on the window object
				if (propertyName in scope) {
					scope[propertyName] = undef;
				}
			}
		}

		function cleanupScriptNode(response) {
			try {
				if (response.raw && response.raw.parentNode) {
					response.raw.parentNode.removeChild(response.raw);
				}
			} catch (e) {
				// ignore
			}
		}

		function registerCallback(prefix, resolve, response, name) {
			if (!name) {
				do {
					name = prefix + Math.floor(new Date().getTime() * Math.random());
				}
				while (name in global);
			}

			global[name] = function jsonpCallback(data) {
				response.entity = data;
				clearProperty(global, name);
				cleanupScriptNode(response);
				if (!response.request.canceled) {
					resolve(response);
				}
			};

			return name;
		}

		/**
		 * Executes the request as JSONP.
		 *
		 * @param {string} request.path the URL to load
		 * @param {Object} [request.params] parameters to bind to the path
		 * @param {string} [request.callback.param='callback'] the parameter name for
		 *   which the callback function name is the value
		 * @param {string} [request.callback.prefix='jsonp'] prefix for the callback
		 *   function, as the callback is attached to the window object, a unique,
		 *   unobtrusive prefix is desired
		 * @param {string} [request.callback.name=<generated>] pins the name of the
		 *   callback function, useful for cases where the server doesn't allow
		 *   custom callback names. Generally not recommended.
		 *
		 * @returns {Promise<Response>}
		 */
		return client(function jsonp(request) {
			return new responsePromise.ResponsePromise(function (resolve, reject) {

				var callbackName, callbackParams, script, firstScript, response;

				request = typeof request === 'string' ? { path: request } : request || {};
				response = { request: request };

				if (request.canceled) {
					response.error = 'precanceled';
					reject(response);
					return;
				}

				request.callback = request.callback || {};
				callbackName = registerCallback(request.callback.prefix || 'jsonp', resolve, response, request.callback.name);
				callbackParams = {};
				callbackParams[request.callback.param || 'callback'] = callbackName;

				request.canceled = false;
				request.cancel = function cancel() {
					request.canceled = true;
					cleanupScriptNode(response);
					reject(response);
				};

				script = document.createElement('script');
				script.type = 'text/javascript';
				script.async = true;
				script.src = new UrlBuilder(request.path, request.params).build(callbackParams);

				function handlePossibleError() {
					if (typeof global[callbackName] === 'function') {
						response.error = 'loaderror';
						clearProperty(global, callbackName);
						cleanupScriptNode(response);
						reject(response);
					}
				}
				script.onerror = function () {
					handlePossibleError();
				};
				script.onload = script.onreadystatechange = function (e) {
					// script tag load callbacks are completely non-standard
					// handle case where onreadystatechange is fired for an error instead of onerror
					if ((e && (e.type === 'load' || e.type === 'error')) || script.readyState === 'loaded') {
						handlePossibleError();
					}
				};

				response.raw = script;
				firstScript = document.getElementsByTagName('script')[0];
				firstScript.parentNode.insertBefore(script, firstScript);

			});
		});

	});

}(
	typeof define === 'function' && define.amd ? define : function (factory) { module.exports = factory(require); },
	typeof window !== 'undefined' ? window : void 0,
	typeof document !== 'undefined' ? document : void 0
	// Boilerplate for AMD and Node
));