src/cm/media/js/lib/yui/yui_3.10.3/docs/promise/subclass-example.html
author gibus
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<!DOCTYPE html>
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<html lang="en">
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<head>
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    <meta charset="utf-8">
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    <title>Example: Subclassing Y.Promise</title>
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    <link rel="stylesheet" href="http://fonts.googleapis.com/css?family=PT+Sans:400,700,400italic,700italic">
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    <link rel="stylesheet" href="../../build/cssgrids/cssgrids-min.css">
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    <link rel="stylesheet" href="../assets/css/main.css">
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    <link rel="stylesheet" href="../assets/vendor/prettify/prettify-min.css">
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    <link rel="shortcut icon" type="image/png" href="../assets/favicon.png">
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    <script src="../../build/yui/yui-min.js"></script>
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</head>
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<body>
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<!--
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<a href="https://github.com/yui/yui3"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://s3.amazonaws.com/github/ribbons/forkme_right_darkblue_121621.png" alt="Fork me on GitHub"></a>
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-->
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<div id="doc">
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    <div id="hd">
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        <h1><img src="http://yuilibrary.com/img/yui-logo.png"></h1>
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    </div>
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        <a href="#toc" class="jump">Jump to Table of Contents</a>
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            <h1>Example: Subclassing Y.Promise</h1>
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    <div class="yui3-g">
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        <div class="yui3-u-3-4">
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            <div id="main">
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                <div class="content"><style scoped>
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    .error {
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        background: #ffc5c4;
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    }
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</style>
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<div class="intro">
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    <p>
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        This example expands on the <a href="basic-example.html">Wrapping async transactions with promises</a> example to illustrate how to create your own Promise subclass for performing operations on arrays.
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    </p>
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</div>
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<div class="example yui3-skin-sam">
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    <div id="demo"></div>
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    <script>
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YUI().use('promise', 'jsonp', 'node', 'array-extras', function (Y) {
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function ArrayPromise() {
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    ArrayPromise.superclass.constructor.apply(this, arguments);
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}
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Y.extend(ArrayPromise, Y.Promise);
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// Although Y.Array.each does not return an array, for the purpose of this
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// example we make it chainable by returning the same array
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ArrayPromise.prototype.each = function (fn, thisObj) {
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    return this.then(function (array) {
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        Y.Array.each(array, fn, thisObj);
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        return array;
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    });
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};
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// Y.Array.map returns a new array, so we return the result of this.then()
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ArrayPromise.prototype.map = function (fn, thisObj) {
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    return this.then(function (array) {
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        // By returning the result of Y.Array.map we are returning a new promise
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        // representing the new array
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        return Y.Array.map(array, fn, thisObj);
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    });
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};
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// Y.Array.filter follows the same pattern as Y.Array.map
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ArrayPromise.prototype.filter = function (fn, thisObj) {
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    return this.then(function (array) {
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        return Y.Array.filter(array, fn, thisObj);
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    });
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};
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// Takes any promise and returns an ArrayPromise
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function toArrayPromise(promise) {
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    return new ArrayPromise(function (fulfill, reject) {
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        promise.then(fulfill, reject);
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    });
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}
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// A cache for GitHub user data
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var GitHub = (function () {
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    var cache = {},
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        githubURL = 'https://api.github.com/users/{user}?callback={callback}';
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    function getUserURL(name) {
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        return Y.Lang.sub(githubURL, {
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            user: name
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        });
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    }
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    // Fetches a URL, stores a promise in the cache and returns it
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    function fetch(url) {
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        var promise = new Y.Promise(function (fulfill, reject) {
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            Y.jsonp(url, function (res) {
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                var meta = res.meta,
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                    data = res.data;
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                // Check for a successful response, otherwise reject the
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                // promise with the message returned by the GitHub API.
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                if (meta.status >= 200 && meta.status < 300) {
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                    fulfill(data);
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                } else {
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                    reject(new Error(data.message));
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                }
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            });
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            // Add a timeout in case the URL is completely wrong
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            // or GitHub is too busy
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            setTimeout(function () {
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                // Once a promise has been fulfilled or rejected it will never
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                // change its state again, so we can safely call reject() after
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                // some time. If it was already fulfilled or rejected, nothing will
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                // happen
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                reject(new Error('Timeout'));
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            }, 10000);
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        });
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        // store the promise in the cache object
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        cache[url] = promise;
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        return promise;
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    }
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    return {
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        getUser: function (name) {
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            var url = getUserURL(name);
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            if (cache[url]) {
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                // If we have already stored the promise in the cache we just return it
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                return cache[url];
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            } else {
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                // fetch() will make a JSONP request, cache the promise and return it
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                return fetch(url);
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            }
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        }
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    };
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}());
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var demoNode = Y.one('#demo');
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function log(text) {
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    demoNode.append(Y.Node.create('<div></div>').set('text', text));
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}
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function showError(message) {
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    demoNode.append(
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        Y.Node.create('<div class="error"></div>').set('text', message)
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    );
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}
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log('Fetching GitHub data for users: "yui", "yahoo" and "davglass"...')
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// requests is a regular promise
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var requests = Y.batch(GitHub.getUser('yui'), GitHub.getUser('yahoo'), GitHub.getUser('davglass'));
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// users is now an ArrayPromise
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var users = toArrayPromise(requests);
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// Transform the data into a list of names
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users.map(function (data) {
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    log('Getting name for user "' + data.login + '"...')
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    return data.name;
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}).filter(function (name) {
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    log('Checking if the name "' + name + '" starts with "Y"...')
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    return name.charAt(0) === 'Y';
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}).then(function (names) {
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    log('Done!');
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    return names;
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}).each(function (name, i) {
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    log(i + '. ' + name);
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}).then(null, function (error) {
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    // if there was an error in any step or request, it is automatically
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    // passed around the promise chain so we can react to it at the end
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    showError(error.message);
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});
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});
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</script>
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</div>
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<h2 id="subclassing-ypromise">Subclassing Y.Promise</h2>
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<p>
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    You can subclass a YUI promise with <a href="../yui/yui-extend.html">Y.extend</a> the same way you would any other class. Keep in mind that Promise constructors take a function as a parameter so you need to call the superclass constructor in order for it to work.
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</p>
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<pre class="code prettyprint">function ArrayPromise() {
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    ArrayPromise.superclass.constructor.apply(this, arguments);
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}
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Y.extend(ArrayPromise, Y.Promise);</pre>
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<h2 id="method-chaining">Method Chaining</h2>
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<p>
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    Chaining promise methods is done by returning the result of calling the promise's <code>then()</code> method. <code>then()</code> <strong>always returns a promise of its same kind</strong>, so this will allow us to chain array operations as if they were real arrays.
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</p>
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<p>
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    For the purpose of this example we will only add the <code>each</code>, <code>filter</code> and <code>map</code> methods from the <code>array-extras</code> module.
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</p>
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<pre class="code prettyprint">&#x2F;&#x2F; Although Y.Array.each does not return an array, for the purpose of this
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&#x2F;&#x2F; example we make it chainable by returning the same array
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ArrayPromise.prototype.each = function (fn, thisObj) {
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    return this.then(function (array) {
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        Y.Array.each(array, fn, thisObj);
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        return array;
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    });
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};
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&#x2F;&#x2F; Y.Array.map returns a new array, so we return the result of this.then()
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ArrayPromise.prototype.map = function (fn, thisObj) {
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    return this.then(function (array) {
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        &#x2F;&#x2F; By returning the result of Y.Array.map we are returning a new promise
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        &#x2F;&#x2F; representing the new array
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        return Y.Array.map(array, fn, thisObj);
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    });
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};
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&#x2F;&#x2F; Y.Array.filter follows the same pattern as Y.Array.map
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ArrayPromise.prototype.filter = function (fn, thisObj) {
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    return this.then(function (array) {
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        return Y.Array.filter(array, fn, thisObj);
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    });
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};</pre>
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<p>
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    Finally we need a simple way to take a promise that we know contains an array and create an ArrayPromise with its value.
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</p>
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<pre class="code prettyprint">&#x2F;&#x2F; Takes any promise and returns an ArrayPromise
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function toArrayPromise(promise) {
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    return new ArrayPromise(function (fulfill, reject) {
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        promise.then(fulfill, reject);
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    });
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}</pre>
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<h3 id="putting-our-class-to-action">Putting our Class to Action</h3>
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<p>
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    There are many cases in which you would want to work on asynchronous array values. Performing more than one async operation at a time and dealing with the result is one common use case. <code>Y.batch</code> waits for many operations and returns a promise representing an array with the result of all the operations, so you could wrap it in an ArrayPromise to modify all those results.
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</p>
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<p>
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    We will use the JSONP Cache from <a href="jsonp-cache.html">the previous example</a> and make several simultaneous requests.
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</p>
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<pre class="code prettyprint">log(&#x27;Fetching GitHub data for users: &quot;yui&quot;, &quot;yahoo&quot; and &quot;davglass&quot;...&#x27;)
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&#x2F;&#x2F; requests is a regular promise
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var requests = Y.batch(GitHub.getUser(&#x27;yui&#x27;), GitHub.getUser(&#x27;yahoo&#x27;), GitHub.getUser(&#x27;davglass&#x27;));
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&#x2F;&#x2F; users is now an ArrayPromise
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var users = toArrayPromise(requests);
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&#x2F;&#x2F; Transform the data into a list of names
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users.map(function (data) {
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    log(&#x27;Getting name for user &quot;&#x27; + data.login + &#x27;&quot;...&#x27;)
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    return data.name;
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}).filter(function (name) {
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    log(&#x27;Checking if the name &quot;&#x27; + name + &#x27;&quot; starts with &quot;Y&quot;...&#x27;)
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    return name.charAt(0) === &#x27;Y&#x27;;
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}).then(function (names) {
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    log(&#x27;Done!&#x27;);
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    return names;
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}).each(function (name, i) {
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    log(i + &#x27;. &#x27; + name);
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}).then(null, function (error) {
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    &#x2F;&#x2F; if there was an error in any step or request, it is automatically
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    &#x2F;&#x2F; passed around the promise chain so we can react to it at the end
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    showError(error.message);
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});</pre>
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<h2 id="full-example-code">Full Example Code</h2>
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<pre class="code prettyprint">&lt;script&gt;
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YUI().use(&#x27;promise&#x27;, &#x27;jsonp&#x27;, &#x27;node&#x27;, &#x27;array-extras&#x27;, function (Y) {
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function ArrayPromise() {
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    ArrayPromise.superclass.constructor.apply(this, arguments);
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}
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Y.extend(ArrayPromise, Y.Promise);
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&#x2F;&#x2F; Although Y.Array.each does not return an array, for the purpose of this
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&#x2F;&#x2F; example we make it chainable by returning the same array
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ArrayPromise.prototype.each = function (fn, thisObj) {
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    return this.then(function (array) {
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        Y.Array.each(array, fn, thisObj);
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        return array;
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    });
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};
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&#x2F;&#x2F; Y.Array.map returns a new array, so we return the result of this.then()
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ArrayPromise.prototype.map = function (fn, thisObj) {
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    return this.then(function (array) {
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        &#x2F;&#x2F; By returning the result of Y.Array.map we are returning a new promise
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        &#x2F;&#x2F; representing the new array
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        return Y.Array.map(array, fn, thisObj);
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    });
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};
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&#x2F;&#x2F; Y.Array.filter follows the same pattern as Y.Array.map
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ArrayPromise.prototype.filter = function (fn, thisObj) {
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    return this.then(function (array) {
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        return Y.Array.filter(array, fn, thisObj);
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    });
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};
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&#x2F;&#x2F; Takes any promise and returns an ArrayPromise
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function toArrayPromise(promise) {
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    return new ArrayPromise(function (fulfill, reject) {
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        promise.then(fulfill, reject);
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    });
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}
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&#x2F;&#x2F; A cache for GitHub user data
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var GitHub = (function () {
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    var cache = {},
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        githubURL = &#x27;https:&#x2F;&#x2F;api.github.com&#x2F;users&#x2F;{user}?callback={callback}&#x27;;
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    function getUserURL(name) {
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        return Y.Lang.sub(githubURL, {
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            user: name
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        });
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    }
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    &#x2F;&#x2F; Fetches a URL, stores a promise in the cache and returns it
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    function fetch(url) {
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        var promise = new Y.Promise(function (fulfill, reject) {
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            Y.jsonp(url, function (res) {
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                var meta = res.meta,
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                    data = res.data;
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                &#x2F;&#x2F; Check for a successful response, otherwise reject the
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                &#x2F;&#x2F; promise with the message returned by the GitHub API.
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                if (meta.status &gt;= 200 &amp;&amp; meta.status &lt; 300) {
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                    fulfill(data);
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                } else {
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                    reject(new Error(data.message));
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                }
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            });
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            &#x2F;&#x2F; Add a timeout in case the URL is completely wrong
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            &#x2F;&#x2F; or GitHub is too busy
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            setTimeout(function () {
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                &#x2F;&#x2F; Once a promise has been fulfilled or rejected it will never
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                &#x2F;&#x2F; change its state again, so we can safely call reject() after
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                &#x2F;&#x2F; some time. If it was already fulfilled or rejected, nothing will
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                &#x2F;&#x2F; happen
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                reject(new Error(&#x27;Timeout&#x27;));
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            }, 10000);
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        });
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        &#x2F;&#x2F; store the promise in the cache object
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        cache[url] = promise;
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        return promise;
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    }
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    return {
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        getUser: function (name) {
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            var url = getUserURL(name);
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            if (cache[url]) {
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                &#x2F;&#x2F; If we have already stored the promise in the cache we just return it
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                return cache[url];
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            } else {
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                &#x2F;&#x2F; fetch() will make a JSONP request, cache the promise and return it
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                return fetch(url);
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            }
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        }
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    };
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}());
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var demoNode = Y.one(&#x27;#demo&#x27;);
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function log(text) {
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    demoNode.append(Y.Node.create(&#x27;&lt;div&gt;&lt;&#x2F;div&gt;&#x27;).set(&#x27;text&#x27;, text));
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}
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function showError(message) {
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    demoNode.append(
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        Y.Node.create(&#x27;&lt;div class=&quot;error&quot;&gt;&lt;&#x2F;div&gt;&#x27;).set(&#x27;text&#x27;, message)
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    );
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}
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log(&#x27;Fetching GitHub data for users: &quot;yui&quot;, &quot;yahoo&quot; and &quot;davglass&quot;...&#x27;)
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&#x2F;&#x2F; requests is a regular promise
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var requests = Y.batch(GitHub.getUser(&#x27;yui&#x27;), GitHub.getUser(&#x27;yahoo&#x27;), GitHub.getUser(&#x27;davglass&#x27;));
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&#x2F;&#x2F; users is now an ArrayPromise
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var users = toArrayPromise(requests);
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&#x2F;&#x2F; Transform the data into a list of names
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users.map(function (data) {
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    log(&#x27;Getting name for user &quot;&#x27; + data.login + &#x27;&quot;...&#x27;)
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    return data.name;
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}).filter(function (name) {
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    log(&#x27;Checking if the name &quot;&#x27; + name + &#x27;&quot; starts with &quot;Y&quot;...&#x27;)
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    return name.charAt(0) === &#x27;Y&#x27;;
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}).then(function (names) {
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    log(&#x27;Done!&#x27;);
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    return names;
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}).each(function (name, i) {
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    log(i + &#x27;. &#x27; + name);
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}).then(null, function (error) {
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    &#x2F;&#x2F; if there was an error in any step or request, it is automatically
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    &#x2F;&#x2F; passed around the promise chain so we can react to it at the end
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    showError(error.message);
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});
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});
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&lt;&#x2F;script&gt;</pre>
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</div>
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            </div>
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        </div>
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        <div class="yui3-u-1-4">
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            <div class="sidebar">
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                    <div id="toc" class="sidebox">
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                        <div class="hd">
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                            <h2 class="no-toc">Table of Contents</h2>
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                        </div>
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                        <div class="bd">
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                            <ul class="toc">
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<li>
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<a href="#subclassing-ypromise">Subclassing Y.Promise</a>
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</li>
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<li>
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   444
<a href="#method-chaining">Method Chaining</a>
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<ul class="toc">
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<li>
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<a href="#putting-our-class-to-action">Putting our Class to Action</a>
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</li>
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</ul>
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</li>
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<li>
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<a href="#full-example-code">Full Example Code</a>
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</li>
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</ul>
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                        </div>
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                    </div>
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                    <div class="sidebox">
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                        <div class="hd">
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                            <h2 class="no-toc">Examples</h2>
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                        </div>
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                        <div class="bd">
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                            <ul class="examples">
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                                        <li data-description="Wrapping async transactions with promises">
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                                            <a href="basic-example.html">Wrapping async transactions with promises</a>
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                                        </li>
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   472
                                    
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                                        <li data-description="Extend Y.Promise to create classes that encapsulate standard transaction logic in descriptive method names">
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   476
                                            <a href="subclass-example.html">Subclassing Y.Promise</a>
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                                        </li>
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diff changeset
   478
                                    
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                                        <li data-description="Extend the Promise class to create your own Node plugin that chains transitions">
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   482
                                            <a href="plugin-example.html">Creating a Node Plugin that chains transitions</a>
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   483
                                        </li>
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                            </ul>
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                        </div>
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                    </div>
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            </div>
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        </div>
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    </div>
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</div>
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<script src="../assets/vendor/prettify/prettify-min.js"></script>
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<script>prettyPrint();</script>
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<script>
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YUI.Env.Tests = {
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    examples: [],
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    project: '../assets',
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    assets: '../assets/promise',
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    name: 'subclass-example',
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   506
    title: 'Subclassing Y.Promise',
89ef5ed3c48b Upgrades to yui 3.10.3
gibus
parents:
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    newWindow: '',
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parents:
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    auto:  false 
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parents:
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   509
};
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parents:
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   510
YUI.Env.Tests.examples.push('basic-example');
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parents:
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YUI.Env.Tests.examples.push('subclass-example');
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parents:
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YUI.Env.Tests.examples.push('plugin-example');
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parents:
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   513
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parents:
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</script>
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parents:
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<script src="../assets/yui/test-runner.js"></script>
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gibus
parents:
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   516
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gibus
parents:
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   517
89ef5ed3c48b Upgrades to yui 3.10.3
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parents:
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   518
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parents:
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</body>
89ef5ed3c48b Upgrades to yui 3.10.3
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parents:
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   520
</html>