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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&#x27;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&#x27;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."> {{&gt;key}} </a> </li> <li class=" "> <a class="function" href="can-stache.tags.comment.html" title="A comment that doesn&#x27;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&#x27;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&#x27;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.expressions.html">Expressions</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>Expressions</h1> <div>page</div> </div> <section class="description"> <p>In addition to different magic tag types, stache supports different expression types. These can be used in various combinations to call <a href="can-stache.registerHelper.html" title="Register a helper.">helper methods</a> or <a href="can-component.prototype.ViewModel.html" title="Provides or describes a constructor function that provides values and methods to the component's template. The constructor function is initialized with values specified by the component element's data bindings.">viewModel methods</a>. The following is an example of all the expressions combined:</p> </section> </section> <section class="on-this-page-table"> </section> <section class="title-footer"> <ul class="title-links"> <!-- <li><a href="#">docco</a></li> --> <li><a href="//github.com/canjs/can-stache/tree/v3.0.8/docs/expressions/expressions.md">source</a></li> <!-- <li><a href="#">download</a></li> --> <!-- <li><a href="#">tests</a></li> --> </ul> </section> <section class="body"> <pre><code>{{helper key1 &quot;string&quot; method(key2, 1, prop1=key3) prop2=key4}} </code></pre> <p>There are 6 expression types stache supports:</p> <ul> <li>Literal expressions like <code>{{&quot;string&quot;}}</code></li> <li>KeyLookup expressions like <code>{{key}}</code></li> <li>Hash expressions like <code>{{prop=key}}</code></li> <li>Call expressions like <code>{{method(arg)}}</code></li> <li>Helper expressions like <code>{{helper arg}}</code></li> <li>Bracket expressions like <code>{{[key]}}</code></li> </ul> <h2>Literal expressions</h2> <p>A <a href="can-stache/expressions/literal.html" title="Specify a JavaScript primitive type.">Literal Expression</a> specifies JS primitive values like:</p> <ul> <li>Strings <code>&quot;strings&quot;</code></li> <li>Numbers <code>5</code></li> <li>Booleans <code>true</code> or <code>false</code></li> <li>And <code>null</code> or <code>undefined</code></li> </ul> <p>They are usually passed as arguments to Call or Helper expressions like:</p> <pre><code>{{pluralize &quot;dog&quot; 2}} {{task.filter(&quot;completed&quot;, true)}} </code></pre> <h2>KeyLookup expressions</h2> <p>A <a href="can-stache/expressions/key-lookup.html" title="">KeyLookup Expression</a> specifies a value in the <a href="can-view-scope.html" title="Create a lookup node for keys.">scope</a> or <a href="can-view-scope.Options.html" title="">HelperOptions scope</a> that will be looked up. KeyLookup expressions can be the entire stache expression like:</p> <pre><code>{{key}} </code></pre> <p>Or they can make up the method, helper, arguments, and hash value parts of Call, Helper, and Hash expressions:</p> <pre><code>{{method(arg1,arg2}} Call {{helper arg1 arg2}} Helper {{method( prop=hashValue )}} Hash </code></pre> <p>The value returned up by a KeyLookup depends on what the <a href="can-stache.key.html" title="A named reference to a value in the scope or helper scope in a template.">key</a> looks like, and what expression type the KeyLookup is within.</p> <p>For example, <code>{{method(~./key)}}</code> will call <code>method</code> with a <a href="can-compute.computed.html" title="A derived value from other computes and observable maps.">compute</a> that looks up the value of <code>key</code> only in the top of the <a href="can-view-scope.html" title="Create a lookup node for keys.">scope</a>.</p> <p>The rules are as follows:</p> <ul> <li><strong>call expression arguments</strong> <code>{{method(key)}}</code> - values are passed.</li> <li><strong>helper expression arguments</strong> <code>{{helper key}}</code> - computes are passed.</li> <li><strong>hash value in call expression</strong> <code>{{method(hash=key)}}</code> - values are set as property values.</li> <li><strong>hash value in helper expression</strong> <code>{{method hash=key}}</code> - computes are set as property values.</li> <li><strong>special operator</strong> <code>{{%index}}</code> - lookup values in a special context provided by some helpers.</li> <li><strong>compute operator</strong> <code>{{method(~key)}}</code> - pass a compute instead of a value.</li> <li><strong>at operator</strong> <code>{{method(@key}}</code> - pass a function instead of trying to read the value of the function.</li> <li><strong>current context</strong> <code>{{./key}}</code> - only lookup key at the top of the scope.</li> <li><strong>parent context</strong> <code>{{../key}}</code> - lookup the value in the parent context.</li> <li><strong>context</strong> <code>{{.}}</code> - return the current context/top of the scope.</li> </ul> <h2>Hash expressions</h2> <p>A <a href="can-stache/expressions/hash.html" title="">Hash Expression</a> specifies a property value on a object argument in a call expression and property value on the the hash object in a helper expression's <a href="can-stache.helperOptions.html" title="The options argument passed to a helper function when called by a helper.">helperOptions</a> argument.</p> <p>For example, in a call expression:</p> <pre><code>Template: {{methodA(prop=key)}} {{methodB(propX=key propY='literal', propZ=5)}} Data: { methodA: function(arg){}, methodB: function(arg1, arg2), key: compute(&quot;value&quot;) } </code></pre> <ul> <li><code>methodA</code> will be called with <code>{prop: &quot;value&quot;}</code> as <code>arg</code>.</li> <li><code>methodB</code> will be called with <code>{propX: &quot;value&quot;, propY: 'literal'}</code> as <code>arg1</code> and <code>{propZ: 5}</code> as <code>arg2</code></li> </ul> <p>In a helper expression:</p> <pre><code>Template: {{methodA prop=key}} {{methodB(propX=key propY='literal' propZ=5)}} Data: { methodA: function(options){}, methodB: function(options){}, key: compute(&quot;value&quot;) } </code></pre> <ul> <li><code>methodA</code> will be called with <code>{prop: compute(&quot;value&quot;)}</code> as <code>options.hash</code>.</li> <li><code>methodB</code> will be called with <code>{propX: &quot;value&quot;, propY: 'literal', propZ: 5}</code> as <code>options.hash</code>.</li> </ul> <h2>Call expressions</h2> <p>A <a href="can-stache/expressions/call.html" title="">Call Expression</a> calls a function looked up in the <a href="can-view-scope.html" title="Create a lookup node for keys.">scope</a> followed by the <a href="can-view-scope.Options.html" title="">helpers scope</a>. It looks like:</p> <pre><code>Template: &lt;h1&gt;{{pluralize(type, ages.length)}}&lt;/h1&gt; Data: { pluralize: function(type, count){ return type+(count === 1 ? &quot;&quot; : &quot;s&quot;) }, todos: new List([22,32,42]), type: &quot;age&quot; } Result: &lt;h1&gt;Ages&lt;/h1&gt; </code></pre> <p>Call expression arguments are comma (,) separated. If a Hash expression is an argument, an object with the hash properties and values will be passed. For example:</p> <pre><code>Template: &lt;h1&gt;{{pluralize(word=type count=ages.length)}}&lt;/h1&gt; Data: { pluralize: function(options){ return options.word+(options.count === 1 ? &quot;&quot; : &quot;s&quot;) }, todos: new List([22,32,42]), type: &quot;age&quot; } Result: &lt;h1&gt;Ages&lt;/h1&gt; </code></pre> <h2>Helper expressions</h2> <p>A <a href="can-stache/expressions/helper.html" title="">Helper Expression</a> calls a function looked up in the <a href="can-view-scope.Options.html" title="">helpers scope</a> followed by the <a href="can-view-scope.html" title="Create a lookup node for keys.">scope</a>. It looks like:</p> <pre><code>Template: &lt;h1&gt;{{pluralize type ages.length}}&lt;/h1&gt; Data: { pluralize: function(type, count){ return &quot;data-pluralize&quot; }, todos: new List([22,32,42]), type: &quot;age&quot; } Helpers: { pluralize: function(type, count){ return type+(count() === 1 ? &quot;&quot; : &quot;s&quot;) } } Result: &lt;h1&gt;Ages&lt;/h1&gt; </code></pre> <p>Helper expression arguments that are observable are passed a compute. This is in contrast to Call expressions that get passed the value.</p> <p>Helper expression arguments are space seperated. If a Hash expression is an argument, the hash properties and values will be added to the helper options object. For example:</p> <pre><code>Template: &lt;h1&gt;{{pluralize word=type count=ages.length}}&lt;/h1&gt; Data: { todos: new List([22,32,42]), type: &quot;age&quot; } Helpers: { pluralize: function(helperOptions){ return helperOptions.hash.type+(helperOptions.hash.count() === 1 ? &quot;&quot; : &quot;s&quot;) } } Result: &lt;h1&gt;Ages&lt;/h1&gt; </code></pre> <h2>Bracket expressions</h2> <p>A <a href="can-stache/expressions/bracket.html" title="">Bracket Expression</a> can be used to look up a dynamic property in the <a href="can-view-scope.html" title="Create a lookup node for keys.">scope</a>. This looks like:</p> <pre><code>Template: &lt;h1&gt;{{[key]}}&lt;/h1&gt; Data: { key: &quot;name&quot;, name: &quot;Kevin&quot; } Result: &lt;h1&gt;Kevin&lt;/h1&gt; </code></pre> <p>This can be useful for looking up values using keys containing non-alphabetic characters:</p> <pre><code>Template: &lt;h1&gt;{{[&quot;person:name&quot;]}}&lt;/h1&gt; Data: { &quot;person:name&quot;: &quot;Kevin&quot; } Result: &lt;h1&gt;Kevin&lt;/h1&gt; </code></pre> <p>Bracket expressions can also be used to look up a value in the result of another expression:</p> <pre><code>Template: {{getPerson()[key]}} Data: { key: &quot;name&quot;, getPerson: function() { return { name: &quot;Kevin&quot; }; } } Result: &lt;h1&gt;Kevin&lt;/h1&gt; </code></pre> </section> <script type="text/javascript"> var docObject = {"src":{"path":"node_modules/can-stache/docs/expressions/expressions.md"},"description":"\nIn addition to different magic tag types, stache supports different expression\ntypes. These can be used in various combinations to call [can-stache.registerHelper helper methods]\nor [can-component.prototype.ViewModel viewModel methods]. The following is an example of all the expressions\ncombined:\n","name":"can-stache.expressions","title":"Expressions","type":"page","parent":"can-stache.pages","order":2,"pathToRoot":".."}; </script> </article> <footer><p>CanJS is part of <a href="http://donejs.com" target="_blank">DoneJS</a>. 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