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<!DOCTYPE html>  <html lang="en"> <head> <meta charset="utf-8"> <title>CanJS - compute</title> <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no"> <link rel="stylesheet" type="text/css" href="./static/bundles/bit-docs-site/static.css"> <link rel="shortcut icon" sizes="16x16 24x24 32x32 48x48 64x64" href="/docs/images/canjs_favicon.ico"> <link rel="apple-touch-icon" sizes="57x57" href="../docs/images/canjs_favicon_57x57.png"> <link rel="apple-touch-icon-precomposed" sizes="57x57" href="../docs/images/canjs_favicon_57x57.png"> <link rel="apple-touch-icon" sizes="72x72" href="../docs/images/canjs_favicon_72x72.png"> <link rel="apple-touch-icon" sizes="114x114" href="../docs/images/canjs_favicon_114x114.png"> <link rel="apple-touch-icon" sizes="120x120" href="../docs/images/canjs_favicon_128x128.png"> <link rel="apple-touch-icon" sizes="144x144" href="../docs/images/canjs_favicon_144x144.png"> <link rel="apple-touch-icon" sizes="152x152" href="../docs/images/canjs_favicon_152x152.png"> <meta content="yes" name="apple-mobile-web-app-capable"> <meta name="apple-mobile-web-app-status-bar-style" content="white-translucent"> <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','https://www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-2302003-11', 'auto'); ga('send', 'pageview'); </script> </head> <body> <input type="checkbox" id="nav-trigger" class="nav-trigger"/> <label for="nav-trigger">Menu</label> <div id="everything"> <div id="left" class="column"> <div class="top-left"> <div class="brand"> <div class="logo"> <a href="../index.html" alt="CanJS"></a> <div class="dropdown project-dropdown"> <a href="https://donejs.com/">DoneJS</a> <a href="http://stealjs.com/">StealJS</a> <a href="http://jquerypp.com/">jQuery ++</a> <a href="https://funcunit.com/">FuncUnit</a> <a href="http://documentjs.com/">DocumentJS</a> </div> </div> <div class="version"> <div class="version-number"> 3.0.0 </div> <div class="dropdown version-dropdown"> <a href="https://v2.canjs.com">2.3.27</a> </div> </div> </div> <div class="search-bar"> <p>   </p> </div> </div> <div class="bottom-left"> <div class="social-side-container"> <ul class="social-side"> <li> <a class="header-mobile github" href="https://github.com/canjs/canjs" target="_blank"><img class="social-icon-small" src="../docs/images/github.png">Github</a> </li> <li> <a class="header-mobile twitter" href="https://twitter.com/canjs" target="_blank"><img class="social-icon-small" src="../docs/images/twitter.png">Twitter</a> </li> </ul> <ul class="social-side"> <li> <a class="header-mobile" href="https://gitter.im/canjs/canjs" target="_blank">Chat</a> </li> <li> <a class="header-mobile" href="http://forums.donejs.com/c/canjs" target="_blank">Forum</a> </li> </ul> </div> <ul> <li class=" "> <a class="page" href="guides.html" title="Welcome to CanJS! 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This may trigger a <code>"change"</code> event that can be listened for with [can-computed.bind].</p> <p>If the compute is called without any arguments (<code>compute()</code>), it simply returns the current value.</p> </li> </ol> </div> <div class="returns"> <h3 class="returns-title">Returns</h3> <p> <code>{*}</code>: <p>The current value of the compute.</p> </p> </div> </div> <section class="body"> <h2>Use</h2> <p>A compute instance is created with <a href="can-compute.html" title="Create an observable value.">can-compute</a> and used as an observable value. Computes are useful to provide a value representative of multiple other observables:</p> <pre><code class="language-js">var person = new Person({ first: "Matthew", last: "Phillips" }); var fullName = compute(function(){ return person.first + " " + person.last; }); console.log(fullName()); // -> "Matthew Phillips". </code></pre> <p>Calling the compute with a value will cause it to run as a setter function:</p> <pre><code class="language-js">var count = compute(0); console.log(count()); // -> 0 count(5); console.log(count()); // -> 5 </code></pre> <p>This depends on how the <a href="can-compute.html" title="Create an observable value.">getterSetter</a> is defined, and can adjust how it handles setters:</p> <pre><code class="language-js">var plusOne = compute(function(val){ if(val) { return val + 1; } else { return 1; } }); console.log(plusOne()); // -> 1 plusOne(5); console.log(plusOne()); // -> 6 </code></pre> </section> <script type="text/javascript"> var docObject = {"src":{"path":"node_modules/can-compute/docs/computed.md"},"description":"A derived value from other computes and observable maps. \n","title":"compute","name":"can-compute.computed","type":"function","parent":"can-compute","signatures":[{"code":"compute([newVal])","description":"\n\nGets the compute's value if no arguments are provided, otherwise calls the compute's setter with the value passed as the first argument.\n","params":[{"types":[{"type":"*"}],"optional":true,"name":"newVal","description":"If the compute is called with an argument, the first argument is used\nto set the compute to a new value. 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