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<!DOCTYPE html>  <html lang="en"> <head> <meta charset="utf-8"> <title>CanJS - helper</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=" "> <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="current parent expanded"> <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.helper.html">helper</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>helper</h1> <div>typedef</div> </div> <section class="description"> <p>A helper function passed to <a href="can-stache.registerHelper.html" title="Register a helper.">registerHelper</a>. 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.</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-stache/tree/v3.0.8/docs/helper.md">source</a></li>   </ul> </section> <div class="signature"> <h2 class="signature-title"> <code>function(arg..., <a href="can-stache.helperOptions.html" title="The options argument passed to a helper function when called by a helper.">options</a>)</code> </h2> <div class="parameters"> <h3 class="parameters-title">Parameters</h3> <ol> <li><b>arg</b> <code>{*|<a href="can-compute.html" title="Create an observable value.">can-compute</a>}</code>: <p>Arguments passed from the tag. After the helper name, any space separated <a href="can-stache.key.html" title="A named reference to a value in the scope or helper scope in a template.">keys</a>, numbers or strings are passed as arguments. <a href="can-stache.key.html" title="A named reference to a value in the scope or helper scope in a template.">Keys</a> that read an observable value in <a href="can-stache/expressions/helper.html" title="">helpers</a> are passed as <a href="can-compute.computed.html" title="A derived value from other computes and observable maps.">compute</a>s .</p> </li> <li><b>options</b> <code>{<a href="can-stache.helperOptions.html" title="The options argument passed to a helper function when called by a helper.">helperOptions</a>}</code>: <p>An options object that is an additional argument in <code>Helper</code> expressions that is populated with optional:</p> <ul> <li><code>fn</code> and <code>inverse</code> section rendering functions</li> <li>a <code>hash</code> object of the maps passed to the helper</li> </ul> </li> </ol> </div> <div class="returns"> <h3 class="returns-title">Returns</h3> <p> <code>{documentFragment|String|Array|function(Node)}</code>: <p>The content to be inserted into the template or a callback function. The content can be a:</p> <ul> <li><code>documentFragment</code> like those returned by <a href="can-stache.helperOptions.html" title="The options argument passed to a helper function when called by a helper.">helperOptions</a>.fn.</li> <li><code>String</code> like <code>"Hello World"</code></li> <li><code>Array</code> of strings and nodes like <code>["Hello", document.createElement('div')]</code></li> </ul> <p>If a <code>function(Node)</code> is returned, it will be called back with an HTML Element or text node.</p> <p>If the helper is called on an element like:</p> <pre><code><div {{myHelper}}> </code></pre> <p>... the callback function will be called with the <code>div</code>.</p> <p>If the helper is called outside of an element's tag like:</p> <pre><code><div> {{myHelper}} </div> </code></pre> <p>... the callback function will be called with a placeholder text node.</p> </p> </div> </div> <section class="body"> <h2>Returning an element callback function</h2> <p>If a helper returns a function, that function is called back after the template has been rendered into DOM elements. This can be used to create stache tags that have rich behavior.</p> <p>If the helper is called <strong>within a tag</strong> like:</p> <pre><code><ul {{sortable}}/> </code></pre> <p>The returned function is called with the <code><ul></code> element:</p> <pre><code>stache.registerHelper("sortable",function(){ return function(el){ $(el).slider(); } }); </code></pre> <p>If the helper is called <strong>between tags</strong> like:</p> <pre><code><ul>{{items}}</ul> </code></pre> <p>The returned function is called with a temporary text node:</p> <pre><code>stache.registerHelper("items",function(){ return function(textNode){ // do something, probably replace textNode } }); </code></pre> <p>While this form of helper is still supported, it's more common to create similar functionality with <a href="can-component.html" title="Create a custom element that can be used to manage widgets or application logic.">can-component</a> or <a href="can-view-callbacks.html" title="Registered callbacks for behaviors">can-view-callbacks</a>.</p> </section> <script type="text/javascript"> var docObject = {"src":{"path":"node_modules/can-stache/docs/helper.md"},"description":"A helper function passed to [can-stache.registerHelper]. \nGiven the arguments, returns the content that should be shown in the DOM\nor a function that will be called on the DOM element the helper was\ncalled on.\n\n","type":"typedef","title":"helper","types":[{"type":"function","returns":{"types":[{"type":"documentFragment"},{"type":"String"},{"type":"Array"},{"type":"function","returns":{"types":[{"type":"undefined"}]},"params":[{"types":[{"type":"Node"}]}]}],"description":"The content to be inserted into the template or a callback function. 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The content can be a:\n\n - `documentFragment` like those returned by [can-stache.helperOptions].fn.\n - `String` like `\"Hello World\"`\n - `Array` of strings and nodes like `[\"Hello\", document.createElement('div')]`\n\nIf a `function(Node)` is returned, it will be called back with an HTML Element or text node. \n\nIf the helper is called on an element like:\n\n```\n<div {{myHelper}}>\n```\n\n... the callback function will be called with the `div`. \n\nIf the helper is called\noutside of an element's tag like:\n\n```\n<div> {{myHelper}} </div>\n```\n\n... the callback function will be called with a placeholder text node. \n\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>