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 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 ).
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();
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();
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();
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();
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.
<div id="demo">
<input type="button" id="start" value="Start polling">
<input type="button" id="stop" value="Stop polling">
<div id="out">
</div>
</div>
<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>