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<!DOCTYPE html>  <html lang="en"> <head> <meta charset="utf-8"> <title>CanJS - Scope and Context</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=" "> <a class="module" href="can-compute.html" title="Create an observable value."> can-compute </a> </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=" parent expanded"> <a class="module" href="can-stache.html" title="Live binding Mustache and Handlebars-compatible templates."> can-stache </a> <ul> <li> <span>Pages</span> <ul> <li class=" "> <a class="page" href="can-stache.magicTagTypes.html" title=""> Magic Tag Types </a> </li> <li class="current parent expanded"> <a class="page" href="can-stache.scopeAndContext.html" title=""> Scope and Context </a> </li> <li class=" "> <a class="page" href="can-stache.expressions.html" title="In addition to different magic tag types, stache supports different expression types. These can be used in various combinations to call helper methods or viewModel methods. The following is an example of all the expressions combined:"> Expressions </a> </li> <li class=" "> <a class="page" href="can-stache.Acquisition.html" title="There are number of ways to acquire templates such as: raw text, a module loader, or script tags in the markup."> Template Acquisition </a> </li> <li class=" "> <a class="page" href="can-stache.Helpers.html" title="Helpers are functions that can be registered and called from within templates. These functions are typically used to provide functionality that is more appropriate for the view than the viewModel."> Helpers </a> </li> <li class=" "> <a class="page" href="can-stache.Binding.html" title="Live binding refers to templates which update themselves when their state or data changes. can-stache templates are able to listen to observables (like map, list, and can-compute) changing and update the page to reflect those changes."> Live Binding </a> </li> </ul> </li> <li> <span>Methods</span> <ul> <li class=" "> <a class="function" href="can-stache.from.html" title="Return a template loaded from an element."> from </a> </li> <li class=" "> <a class="function" href="can-stache.registerConverter.html" title="Register a helper for bidirectional value conversion."> registerConverter </a> </li> <li class=" "> <a class="function" href="can-stache.registerHelper.html" title="Register a helper."> registerHelper </a> </li> <li class=" "> <a class="function" href="can-stache.registerPartial.html" title="Register a partial. Register a partial template that can be rendered with can-stache.tags.partial."> registerPartial </a> </li> <li class=" "> <a class="function" href="can-stache.registerSimpleHelper.html" title="Register a helper that gets passed values."> registerSimpleHelper </a> </li> <li class=" "> <a class="function" href="can-stache.safeString.html" title="Indicate that a string does not need to be escaped to be safely inserted into the page."> safeString </a> </li> </ul> </li> <li> <span>Tags</span> <ul> <li class=" "> <a class="function" href="can-stache.tags.escaped.html" title="Insert the value of the expression into the output of the template."> {{expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.tags.unescaped.html" title="Insert the unescaped value of the expression into the output of the template."> {{{expression}}} </a> </li> <li class=" "> <a class="function" href="can-stache.tags.section.html" title="Renders a subsection one or more times depending on the type of expression or the expression's return value."> {{#expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.tags.close.html" title=""> {{/expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.tags.inverse.html" title="Like can-stache.tags.section, but renders the opposite subsection depending on the type of expression or the expression's return value."> {{^expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.tags.partial.html" title="Render another template within the current template."> {{>key}} </a> </li> <li class=" "> <a class="function" href="can-stache.tags.comment.html" title="A comment that doesn't get inserted into the rendered result."> {{!expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.else.html" title=""> {{else}} </a> </li> </ul> </li> <li> <span>Expressions</span> <ul> <li class=" "> <a class="typedef" href="can-stache/expressions/bracket.html" title=""> Bracket Expression </a> </li> <li class=" "> <a class="typedef" href="can-stache/expressions/call.html" title=""> Call Expression </a> </li> <li class=" "> <a class="typedef" href="can-stache/expressions/hash.html" title=""> Hash Expression </a> </li> <li class=" "> <a class="typedef" href="can-stache/expressions/helper.html" title=""> Helper Expression </a> </li> <li class=" "> <a class="typedef" href="can-stache/expressions/key-lookup.html" title=""> KeyLookup Expression </a> </li> <li class=" "> <a class="typedef" href="can-stache/expressions/literal.html" title="Specify a JavaScript primitive type."> Literal Expression </a> </li> </ul> </li> <li> <span>Key Operators</span> <ul> <li class=" "> <a class="typedef" href="can-stache/keys/at.html" title="Return whatever value is at a key, regardless if it's a function or a compute."> @at </a> </li> <li class=" "> <a class="typedef" href="can-stache/keys/compute.html" title="Pass a compute instead of a value if an observable is found within calls."> ~compute </a> </li> <li class=" "> <a class="typedef" href="can-stache/keys/current.html" title="Lookup a value in only the current context."> ./current </a> </li> <li class=" "> <a class="typedef" href="can-stache/keys/parent.html" title="Start looking for values in the parent context."> ../parent </a> </li> <li class=" "> <a class="typedef" href="can-stache/keys/special.html" title="Event bindings and some helpers like can-stache.helpers.each provide special values that start with % to prevent potential collisions with other values."> %special </a> </li> <li class=" "> <a class="typedef" href="can-stache/keys/this.html" title="Write out or return the current context."> this </a> </li> <li class=" "> <a class="typedef" href="can-stache/keys/variable.html" title="Store a variable local to the template."> *variable </a> </li> <li class=" "> <a class="typedef" href="can-stache.key.html" title="A named reference to a value in the scope or helper scope in a template."> key </a> </li> </ul> </li> <li> <span>Helpers</span> <ul> <li class=" "> <a class="function" href="can-stache.helpers.if.html" title="can-stache.helpers.if"> {{#if expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.unless.html" title=""> {{#unless expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.each.html" title=""> {{#each expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.with.html" title="Changes the context within a block."> {{#with expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.log.html" title=""> {{log}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.is.html" title="Render something if two values are equal."> {{#is expressions}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.switch.html" title=""> {{#switch expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.case.html" title=""> {{#case expression}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.default.html" title=""> {{#default}} </a> </li> <li class=" "> <a class="function" href="can-stache.helpers.joinBase.html" title=""> {{joinBase expressions}} </a> </li> </ul> </li> <li> <span>Types</span> <ul> <li class=" "> <a class="typedef" href="can-stache.getterSetter.html" title="The getterSetter argument passed to registerConverter."> getterSetter </a> </li> <li class=" "> <a class="typedef" href="can-stache.helper.html" title="A helper function passed to can-stache.registerHelper. Given the arguments, returns the content that should be shown in the DOM or a function that will be called on the DOM element the helper was called on."> helper </a> </li> <li class=" "> <a class="typedef" href="can-stache.helperOptions.html" title="The options argument passed to a helper function when called by a helper."> helperOptions </a> </li> <li class=" "> <a class="typedef" href="can-stache.renderer.html" title="A function returned by can-stache that renders a template into an html documentFragment."> renderer </a> </li> <li class=" "> <a class="typedef" href="can-stache.sectionRenderer.html" title="Renders a section. These functions are usually provided as .fn and .inverse on a stache helper's options."> sectionRenderer </a> </li> <li class=" "> <a class="typedef" href="can-stache.simpleHelper.html" title="A helper function passed to can-stache.registerSimpleHelper."> simpleHelper </a> </li> </ul> </li> </ul> </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-stache.html">can-stache</a></li> / <li><a href="can-stache.scopeAndContext.html">Scope and Context</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>Scope and Context</h1> <div>page</div> </div> <section class="description"> </section> </section> <section class="on-this-page-table"> </section> <section class="title-footer"> <ul class="title-links">  <li><a href="//github.com/canjs/can-stache/tree/v3.0.8/docs/context.md">source</a></li>   </ul> </section> <section class="body"> <p>Every part of a stache template is rendered with a given <a href="can-view-scope.html" title="Create a lookup node for keys.">scope</a>. The scope is used to lookup values. A scope can contain multiple places to lookup values. Each of those places is called a <code>context</code>.</p> <p>This is very similar to how <code>last</code> is looked up in the following JavaScript:</p> <pre><code class="language-js">var message = "Hello" function outer(){ var last = "Abril"; function inner(){ var first = "Alexis"; console.log(message + " "+ first + " " + last); } inner(); } outer(); </code></pre> <p>JavaScript looks for <code>last</code> looks in the <code>inner</code> context and then walks up the scope to the <code>outer</code> context to find a <code>last</code> variable.</p> <p>Lets look at what happens with the scope the following example:</p> <pre><code>Template: <h1>{{message}} {{#person}}{{first}} {{last}}{{/person}}</h1> Data: { person: {first: "Alexis"}, last: "Abril", message: "Hello" } Result: <h1>Hello Alexis Abril</h1> </code></pre> <ol> <li>The template is rendered with <code>Data</code> as the only item in the scope. <code>scope:[Data]</code></li> <li><code>{{message}}</code> is looked up within <code>Data</code>.</li> <li><code>{{#person}}</code> adds the <code>person</code> context to the top of the scope. <code>scope:[Data,Data.person]</code></li> <li><code>{{first}}</code> is looked up in the scope. It will be found on <code>Data.person</code>.</li> <li><code>{{last}}</code> is looked up in the scope. <ol> <li><code>last</code> is looked in <code>Data.person</code>, it's not found.</li> <li><code>last</code> is looked up in <code>Data</code> and returned.</li> </ol></li> <li><code>{{/person}}</code> removes <code>person</code> from the scope. <code>scope:[Data]</code></li> </ol> <p>The context used to lookup a value can be controlled with adding <code>../</code> or <code>./</code> before a key. For instance, if we wanted to make sure <code>last</code> was only going to lookup on <code>person</code>, we could change the template to:</p> <pre><code>Template: <h1>{{message}} {{#person}}{{first}} {{./last}}{{/person}}</h1> Data: { person: {first: "Alexis"}, last: "Abril", message: "Hello" } Result: <h1>Hello Alexis </h1> </code></pre> <p><a href="can-stache.tags.section.html" title="Renders a subsection one or more times depending on the type of expression or the expression's return value.">Sections</a>, <a href="can-stache.Helpers.html" title="Helpers are functions that can be registered and called from within templates. These functions are typically used to provide functionality that is more appropriate for the view than the viewModel.">Helpers</a>, and <a href="can-component.html" title="Create a custom element that can be used to manage widgets or application logic.">custom elements</a> can modify the scope used to render a subsection.</p> <p><a href="can-stache.key.html" title="A named reference to a value in the scope or helper scope in a template.">key</a> modifiers like <code>../</code> and <code>@key</code> can control the context and value that gets returned.</p> </section> <script type="text/javascript"> var docObject = {"src":{"path":"node_modules/can-stache/docs/context.md"},"description":"\n","name":"can-stache.scopeAndContext","title":"Scope and Context","type":"page","parent":"can-stache.pages","order":1,"comment":" ","pathToRoot":".."}; </script> </article> <footer><p>CanJS is part of <a href="http://donejs.com" target="_blank">DoneJS</a>. 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