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<div id="right" class="column"> <div class="top-right"> <div class="top-right-top"> <ul class="top-right-bitovi"> <li class="dropdown"> <a href="http://bitovi.com" class="bitovi icon-bits">Bitovi</a> <ul class="dropdown-menu"> <li><a href="http://bitovi.com">Bitovi.com</a></li> <li><a href="http://bitovi.com/blog/">Blog</a></li> <li><a href="http://bitovi.com/consulting/">Consulting</a></li> <li><a href="http://bitovi.com/training/">Training</a></li> <li><a href="http://bitovi.com/open-source/">Open Source</a></li> </ul> </li> </ul> <div class="brand"> <div class="logo"> <a href="../index.html" alt="CanJS"></a> </div> </div> <ul class="top-right-links"> <li> <a href="https://gitter.im/canjs/canjs">Chat</a> </li> <li> <a href="http://forums.donejs.com/c/canjs">Forum</a> </li> <li> <a class="github-button nav-social" href="https://github.com/canjs/canjs" data-count-href="/canjs/canjs/stargazers" data-count-api="/repos/canjs/canjs#stargazers_count">Star</a> </li> <li> <a 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src="https://img.shields.io/badge/npm%20package-3.0.2-brightgreen.svg" alt="npm package badge" /> </a> </li> <li> <a class="github-button nav-social" href="https://github.com/canjs/can-map" data-count-href="/canjs/can-map/stargazers" data-count-api="/repos/canjs/can-map#stargazers_count">Star</a> </li> </ul> <ul class="title-links">  <li><a href="//github.com/canjs/can-map/tree/v3.0.2/docs/map.md">source</a></li>   </ul> </section> <div class="signature"> <h2 class="signature-title"> <code>new Map([props])</code> </h2> <p>Creates a new instance of can.Map.</p> <div class="parameters"> <h3 class="parameters-title">Parameters</h3> <ol> <li><b>props</b> <code>{Object}</code>: <p>Properties and values to seed the Observe with.</p> </li> </ol> </div> <div class="returns"> <h3 class="returns-title">Returns</h3> <p> <code>{can.Map}</code>: <p>An instance of <code>can.Map</code> with the properties from <em>props</em>.</p> </p> </div> </div> <div class="signature"> <h2 class="signature-title"> <code>Map.extend([name,] [staticProperties,] instanceProperties)</code> </h2> <p>Creates a new extended constructor function.</p> </div> <section class="body"> <h2>Use</h2> <p>Watch this video to see an example of creating an ATM machine using can.Map:</p> <iframe width="662" height="372" src="https://www.youtube.com/embed/QP9mHyxZNiI" frameborder="0" allowfullscreen></iframe> <p><code>Map</code> provides a way for you to listen for and keep track of changes to objects. When you use the getters and setters provided by <code>Map</code>, events are fired that you can react to. <code>Map</code> also has support for working with deep properties. Observable arrays are also available with <code><a href="can-list.html" title="">can-list</a></code>, which is based on <code>Map</code>.</p> <h2>Working with Observes</h2> <p>To create an Observe, use <code>new Map([props])</code>. This will return a copy of <code>props</code> that emits events when its properties are changed with <code><a href="can-map.prototype.attr.html" title="Get or set properties on a Map.">attr</a></code>.</p> <p>You can read the values of properties on Observes directly, but you should never set them directly. You can also read property values using <code>attr</code>.</p> <pre><code>var aName = {a: 'Alexis'}, map = new can.Map(aName); // Observes are copies of data: aName === map; // false // reading from an Observe: map.attr(); // {a: 'Alexis'} map.a; // 'Alexis' map.attr('a'); // 'Alexis' // setting an Observe's property: map.attr('a', 'Alice'); map.a; // Alice // removing an Observe's property; map.removeAttr('a'); map.attr(); // {} // Don't do this! map.a = 'Adam'; // wrong! </code></pre> <p>Find out more about manipulating properties of a map under [can.Map.prototype.attr attr] and [can.Map.prototype.removeAttr removeAttr].</p> <h2>Listening to changes</h2> <p>The real power of maps comes from being able to react to properties being added, set, and removed. Maps emit events when properties are changed that you can bind to.</p> <p><code>Map</code> has two types of events that fire due to changes on a map:</p> <ul> <li>the <em>change</em> event fires on every change to a map.</li> <li>an event named after the property name fires on every change to that property.</li> </ul> <pre><code>var o = new Map({}); o.bind('change', function(ev, attr, how, newVal, oldVal) { console.log('Something on o changed.'); }); o.bind('a', function(ev, newVal, oldVal) { console.log('a was changed.'); }); o.attr('a', 'Alexis'); // 'Something on o changed.' // 'a was changed.' o.attr({ 'a': 'Alice', // 'Something on o changed.' (for a's change) 'b': 'Bob' // 'Something on o changed.' (for b's change) }); // 'a was changed.' o.removeAttr('a'); // 'Something on o changed.' // 'a was changed.' </code></pre> <p>For more detail on how to use these events, see [can.Map.prototype.bind bind] and [can.Map.prototype.unbind unbind]. There is also a plugin called [can.Map.delegate] that makes binding to specific types of events easier:</p> <pre><code>var o = new Map({}); o.delegate('a', 'add', function(ev, newVal, oldVal) { console.log('a was added.'); }); o.delegate('a', 'set', function(ev, newVal, oldVal) { console.log('a was set.'); }); o.delegate('a', 'remove', function(ev, newVal, oldVal) { console.log('a was removed.'); }); o.delegate('a', 'change', function(ev, newVal, oldVal) { console.log('a was changed.'); }); o.attr('a', 'Alexis'); // 'a was added.' // 'a was changed.' o.attr('a', 'Alice'); // 'a was set.' // 'a was changed.' o.removeAttr('a'); // 'a was removed.' // 'a was changed.' </code></pre> <h2>Object.prototype.watch</h2> <p>Due to a method available on the base Object prototype called "watch", refrain from using properties with the same name on Gecko based browsers as there will be a collision. <a 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