can

<!DOCTYPE html>  <html lang="en"> <head> <meta charset="utf-8"> <title>CanJS - async</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! These guides are here to help you develop and improve your relationship with CanJS. After all, picking a JavaScript framework is a commitment. We want CanJS to be the framework you marry. This page helps you know how advance through the different stages of this relationship:"> Guides </a> </li> <li class=" parent expanded"> <a class="page" href="can-core.html" title="The best, most hardened and generally useful libraries in CanJS."> Core </a> <ul> <li class=" "> <a class="module" href="can-component.html" title="Create a custom element that can be used to manage widgets or application logic."> can-component </a> </li> <li class=" parent expanded"> <a class="module" href="can-compute.html" title="Create an observable value."> can-compute </a> <ul> <li class=" "> <a class="typedef" href="can-compute.computeSettings.html" title=""> computeSettings </a> </li> <li class=" "> <a class="function" href="can-compute.computed.html" title="A derived value from other computes and observable maps."> compute </a> </li> </ul> </li> <li class=" "> <a class="module" href="can-connect.html" title="can-connect provides persisted data middleware. Use it to assemble powerful model layers for any JavaScript project."> can-connect </a> </li> <li class=" "> <a class="module" href="can-define.html" title="Exports the define method that defines observable properties and their behavior on a prototype object."> can-define </a> </li> <li class=" "> <a class="module" href="can-define/list/list.html" title="Create observable lists."> can-define/list/list </a> </li> <li class=" "> <a class="module" href="can-define/map/map.html" title="Create observable objects."> can-define/map/map </a> </li> <li class=" "> <a class="function" href="can-route.html" title="Manage browser history and client state by synchronizing the window.location.hash with a map."> can-route </a> </li> <li class=" "> <a class="module" href="can-route-pushstate.html" title="Changes can-route to use pushstate to change the window's pathname instead of the hash. var route = require("can-route-pushstate"); route("{page}", { page: "home" }); route.ready(); route.attr("page", "user"); location.pathname; // -> "/user""> can-route-pushstate </a> </li> <li class=" "> <a class="module" href="can-set.html" title="can-set is a utility for comparing sets that are represented by the parameters commonly passed to service requests."> can-set </a> </li> <li class=" "> <a class="module" href="can-stache.html" title="Live binding Mustache and Handlebars-compatible templates."> can-stache </a> </li> <li class=" "> <a class="module" href="can-stache/helpers/route.html" title="Adds stache helpers that use can-route."> can-stache/helpers/route </a> </li> <li class=" "> <a class="module" href="can-stache-bindings.html" title="Provides template event, one-way, and two-way bindings."> can-stache-bindings </a> </li> </ul> </li> <li class=" "> <a class="page" href="can-ecosystem.html" title="Useful libraries that extend or add important features to the core collection."> Ecosystem </a> </li> <li class=" "> <a class="page" href="can-infrastructure.html" title="Utility libraries that power the core and ecosystem collection."> Infrastructure </a> </li> <li class=" "> <a class="page" href="can-legacy.html" title="Former libraries that we still accept patches for, but are not under active development."> Legacy </a> </li> </ul> </div> </div> <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 href="https://twitter.com/canjs" class="twitter-follow-button nav-social" data-show-count="true" data-show-screen-name="false">Follow @canjs</a><script async src="//platform.twitter.com/widgets.js" charset="utf-8"></script> </li> </ul> </div> <div class="breadcrumb"> <li><a href="../index.html">CanJS</a></li> / <li><a href="can-core.html">Core</a></li> / <li><a href="can-compute.html">can-compute</a></li> / <li><a href="can-compute.async.html">async</a></li> <li class="breadcrumb-dropdown">/ <a> On this page</a> <ul class="on-this-page"></ul> </li> <div class="nav-toggle" title="Back to top"></div> </div> </div> <div class="bottom-right"> <article> <section class="title"> <div class="page-type"> <h1>async</h1> <div>function</div> </div> <section class="description"> <p>Create a compute that can set its value after the computed function has been called.</p> </section> </section> <section class="on-this-page-table"> </section> <section class="title-footer"> <ul class="title-links">  <li><a href="//github.com/canjs/can-compute/tree/v3.0.3/docs/async.md">source</a></li>   </ul> </section> <div class="signature"> <h2 class="signature-title"> <code>compute.async(initialValue, computed(currentValue, setValue(newValue) )</code> </h2> <div class="parameters"> <h3 class="parameters-title">Parameters</h3> <ol> <li><b>The</b> <code>{*}</code>: <p>initial value of the compute.</p> </li> <li><b>computed</b> <code>{<a href="can-compute.asyncComputer.html" title="A function that determines a value for an async compute.">asyncComputer</a>(lastSetValue, setVal)}</code>: <p>A function that returns the current value of the compute and can optionally later call its <code>setValue</code> callback to update the value.</p> </li> </ol> </div> <div class="returns"> <h3 class="returns-title">Returns</h3> <p> <code>{<a href="can-compute.computed.html" title="A derived value from other computes and observable maps.">compute</a>(newVal)}</code>: <p>Returns a compute, but a compute that will possibly not have the correct value unless it is bound to.</p> </p> </div> </div> <section class="body"> <h2>Use</h2> <p>The following compute is a live list of todos for a given userId. <code>todos</code> value would alternate between <code>null</code> and a Todo.List as <code>userId</code> changes.</p> <pre><code>var userId = compute(5) var todos = compute.async(null, function(oldTodoList, setValue){ Todo.findAll({ userId: userId() }, function(todos){ setValue(todos) }); return null; }); </code></pre> <p>The following replaces the list in place:</p> <pre><code>var userId = compute(5) var todos = compute.async(new Todo.List(), function(todoList, setValue){ todoList.replace( Todo.findAll({ userId: userId() }) return todoList; }); </code></pre> </section> <script type="text/javascript"> var docObject = {"src":{"path":"node_modules/can-compute/docs/async.md"},"description":"\nCreate a compute that can set its value after the computed function has been called.\n","title":"async","name":"can-compute.async","type":"function","parent":"can-compute","release":"2.1","hide":true,"signatures":[{"code":"compute.async(initialValue, computed(currentValue, setValue(newValue) )","description":"\n","params":[{"types":[{"type":"*"}],"name":"The","description":"initial value of the compute.\n"},{"types":[{"type":"can-compute.asyncComputer"}],"name":"computed","description":"A function \nthat returns the current value of the compute and can optionally later call \nits `setValue` callback to update the value.\n"}],"returns":{"types":[{"type":"can-compute.computed"}],"description":"Returns a compute, but a compute that will \npossibly not have the correct value unless it is bound to.\n"}}],"_curParam":{"types":[{"type":"can-compute.asyncComputer"}],"name":"computed","description":"A function \nthat returns the current value of the compute and can optionally later call \nits `setValue` callback to update the value.\n"},"_curReturn":{"types":[{"type":"can-compute.computed"}],"description":"Returns a compute, but a compute that will \npossibly not have the correct value unless it is bound to.\n"},"comment":" ","pathToRoot":".."}; </script> </article> <footer><p>CanJS is part of <a href="http://donejs.com" target="_blank">DoneJS</a>. Created and maintained by the core <a href="https://donejs.com/About.html#section=section_Team" target="_blank">DoneJS team</a> and <a href="http://bitovi.com" target="_blank">Bitovi</a>. <strong>Currently 3.0.0.</strong></p></footer> </div> </div> </div> <script> steal = { instantiated: { "bundles/bit-docs-site/static.css!$css" : null } }; </script> <script type='text/javascript' data-main="bit-docs-site/static" src="./static/node_modules/steal/steal.production.js"></script> <script async defer src="https://buttons.github.io/buttons.js"></script> </body> </html>