+ This example shows how to create a reusable JSONPRequest for polling as + well as how to configure success and failure callbacks. See the API + docs and user guide for a full listing of available configurations. +
+ ++ For this example, we will use a JSONP service hosted on YUILibrary to fetch information about + a random Gallery module and render some of the information on the page. +
+The data
+The structure of the JavaScript object returned from YUILibrary's JSONP service will look like this:
+ +{
+ modules: [
+ {
+ url: (the url to the module),
+ title: (the title of the module),
+ summary: (short description of the module),
+ ...,
+ owner: {
+ icon: (url to the author's thumb image),
+ fullname: (the author's full name),
+ rank: (YUI Team member?, Contributor? etc),
+ ...
+ }
+ }
+ ],
+ ...
+}
+
+
+We'll use these objects to populate an HTML template with data {placeholder}s using Y.Lang.sub( template, object ).
Start simple
+To make a single call to the YUILibrary Gallery API, we can just use
+ +Y.jsonp("http://yuilibrary.com/gallery/api/random?callback={callback}", handleJSONP);
+
+
+But since each call to Y.jsonp() creates a new instance of Y.JSONPRequest, we may as well store the instance and reuse it.
var gallery = new Y.JSONPRequest("http://yuilibrary.com/gallery/api/random?callback={callback}", handleJSONP);
+
+gallery.send();
+
+
+Add polling
+JSONPRequest doesn't have any built-in polling mechanism, but Y.later() can handle this for us.
var url = "http://yuilibrary.com/gallery/api/random?callback={callback}";
+
+function handleJSONP(response) {
+ // populate template from the response object and add to the output div
+ ...
+
+ Y.one("#out").setHTML( Y.Lang.sub(template, module) );
+
+ // After 7 seconds, call the API for a new module
+ Y.later(7000, this, this.send);
+};
+
+var gallery = new Y.JSONPRequest(url, handleJSONP);
+gallery.send();
+
+
+Add failure protection
+In case the Gallery API is busy or some other problem arises, we'll also want to handle this case and display an error. We can do this by passing a configuration object as the second parameter rather than a simple success callback.
+ +var gallery = new Y.JSONPRequest(url, {
+ on: {
+ success: function (response) {
+ // populate output div from the template and response object
+ ...
+
+ Y.one("#out").setHTML( Y.Lang.sub(template, module) );
+
+ // After 7 seconds, call the API for a new module
+ Y.later(7000, this, this.send);
+ },
+
+ failure: function () {
+ Y.one("#out").setHTML( failureTemplate );
+ }
+ }
+ });
+
+gallery.send();
+
+
+Add flare
+Now we'll add a bit of flourish, by adding a visual indicator of how long until the next module is requested. We'll replace the call to Y.later() with a call to node.transition() using a shrinking border to show the remaining time. Then when the transition is complete, we call send() again.
+
+
var gallery = new Y.JSONPRequest(url, {
+ on: {
+ success: function (response) {
+ // populate output div from the template and response object
+ ...
+
+ Y.one("#out").setHTML( Y.Lang.sub(template, module) );
+
+ // Add some flare to the poll interval by showing a "time left"
+ // indicator via the header's border
+ Y.one("#out h4")
+ .setStyle("borderRightWidth", "100px")
+ .transition({
+ borderRightWidth: 0,
+ duration: 7
+ }, function () {
+ gallery.send();
+ });
+ },
+
+ failure: function () {
+ Y.one("#out").setHTML( failureTemplate );
+ }
+ }
+ });
+
+gallery.send();
+
+
+Stop the poll
+The final step is to add the ability to start and stop the polling. We'll manage this by adding a property to the gallery JSONPRequest instance named gallery.polling. See the full code listing below for the implementation.
+
+
Full Code Listing
+HTML
+<div id="demo"> + <input type="button" id="start" value="Start polling"> + <input type="button" id="stop" value="Stop polling"> + <div id="out"> + </div> +</div>+ + +
JavaScript
+<script>
+YUI().use("jsonp", "transition",function (Y) {
+
+ var url = "http://yuilibrary.com/gallery/api/random?callback={callback}",
+ outputDiv = Y.one("#out"),
+ gallery;
+
+ // Using the configuration object syntax
+ gallery = new Y.JSONPRequest(url, {
+ on: {
+ success: function (response) {
+ var module = response.modules[0],
+ author = module.owner;
+
+ // Some users don't have a rank
+ if (!author.rank) {
+ author.rank = "user";
+ }
+
+ // Format the author info and store as a property of the
+ // module object for use by Y.Lang.sub
+ // ('this' refers to the JSONPRequest object by default)
+ module.authorHTML = Y.Lang.sub(this.authorTemplate, author);
+
+ outputDiv.setHTML(Y.Lang.sub(this.moduleTemplate, module));
+
+ // Add some flare to the poll interval by showing a "time left"
+ // indicator via the header's border
+ Y.one("#out h4")
+ .setStyle("borderRightWidth", "100px")
+ .transition({
+ borderRightWidth: 0,
+ duration: 7
+ }, function () {
+ if (gallery.polling) {
+ gallery.send();
+ }
+ });
+ },
+
+ failure: function () {
+ gallery.polling = false;
+ outputDiv.setHTML(this.failureTemplate);
+
+ // Wire up the Try again button
+ outputDiv.one("button").on("click", function () {
+ gallery.send();
+ });
+ }
+ }
+ });
+
+
+ gallery.moduleTemplate =
+ '<h4><a href="{url}">{title}</a></h4>' +
+ '<p class="author">{authorHTML}</p>' +
+ '<div>{summary}</div>';
+
+ gallery.authorTemplate =
+ '<img src="{icon}" height="30" width="30">' +
+ ' {fullname} <span class="rank">({rank})</span>';
+
+ gallery.failureTemplate =
+ '<p class="error">Ack, I couldn\'t reach the Gallery web service!</p>' +
+ '<button>Try again</button>';
+
+ gallery.polling = false;
+
+
+ // Click the button to send the JSONP request
+ Y.one("#start").on("click", function (e) {
+ if (!gallery.polling) {
+ gallery.polling = true;
+ gallery.send();
+ }
+ });
+
+ Y.one("#stop").on("click", function (e) {
+ gallery.polling = false;
+ });
+
+});
+</script>
+
+