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<!DOCTYPE html>  <html lang="en"> <head> <meta charset="utf-8"> <title>CanJS - registerConverter</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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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="current parent expanded"> <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.registerConverter.html">registerConverter</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>registerConverter</h1> <div>function</div> </div> <section class="description"> <p>Register a helper for bidirectional value conversion.</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/registerConverter.md">source</a></li>   </ul> </section> <div class="signature"> <h2 class="signature-title"> <code>stache.registerConverter(converterName, getterSetter)</code> </h2> <p>Creates a helper that can do two-way conversion between two values. This is especially useful with <a href="can-stache-bindings.twoWay.html" title="Two-way bind a value in the viewModel or the element to the parent scope.">{($two-way)} bindings</a> like:</p> <pre><code class="language-handlebars"><input {($value)}='numberToString(~age)'/> </code></pre> <p>A converter helper provides:</p> <ul> <li>a <code>get</code> method that returns the value of the <code>left</code> value given the arguments passed on the <code>right</code>.</li> <li>a <code>set</code> method that updates one or multiple of the <code>right</code> arguments computes given a new <code>left</code> value.</li> </ul> <p><code>numberToString</code> might converts a number (<code>age</code>) to a string (<code>value</code>), and the string (<code>value</code>) to a number (<code>age</code>) as follows:</p> <pre><code class="language-js">stache.registerConverter("numberToString", { get: function(fooCompute) { return "" + fooCompute(); }, set: function(newVal, fooCompute) { fooCompute(+newVal); } }); </code></pre> <div class="parameters"> <h3 class="parameters-title">Parameters</h3> <ol> <li><b>converterName</b> <code>{String}</code>: <p>The name of the converter helper.</p> </li> <li><b>getterSetter</b> <code>{<a href="can-stache.getterSetter.html" title="The getterSetter argument passed to registerConverter.">getterSetter</a>}</code>: <p>An object containing get() and set() functions.</p> </li> </ol> </div> </div> <section class="body"> <h2>Use</h2> <p>These helpers are useful for avoiding creating <a href="can-define/map/map.html" title="Create observable objects.">can-define/map/map</a> getters and setters that do similar conversions on the view model. Instead, a converter can keep your viewModels more ignorant of the demands of the view. Especially as the view's most common demand is that everything must be converted to a string.</p> <p>That being said, the following is a richer example of a converter, but one that should probably be part of a view model.</p> <pre><code class="language-handlebars"><input {($value)}='fullName(~first, ~last)'/> </code></pre> <p>The following might converts both ways <code>first</code> and <code>last</code> to <code>value</code>.</p> <pre><code class="language-js">var canBatch = require("can-event/batch/batch"); stache.registerConverter("fullName", { get: function(first, last) { return first() + last(); }, set: function(newFullName, first, last) { canBatch.start(); var parts = newFullName.split(" "); first(parts[0]); last(parts[1]); canBatch.stop(); } }); </code></pre> </section> <script type="text/javascript"> var docObject = {"src":{"path":"node_modules/can-stache/docs/registerConverter.md"},"description":"Register a helper for bidirectional value conversion. \n","title":"registerConverter","name":"can-stache.registerConverter","type":"function","parent":"can-stache.static","signatures":[{"code":"stache.registerConverter(converterName, getterSetter)","description":"\n\nCreates a helper that can do two-way conversion between two\nvalues. This is especially useful with\n[can-stache-bindings.twoWay {($two-way)} bindings] like:\n\n```handlebars\n<input {($value)}='numberToString(~age)'/>\n```\n\nA converter helper provides:\n\n - a `get` method that returns the value\n of the `left` value given the arguments passed on the `right`.\n - a `set` method that updates one or multiple of the `right` arguments\n computes given a new `left` value.\n\n`numberToString` might converts a number (`age`)\nto a string (`value`), and the string (`value`) to a number (`age`)\nas follows:\n\n\n```js\nstache.registerConverter(\"numberToString\", {\n get: function(fooCompute) {\n \treturn \"\" + fooCompute();\n },\n set: function(newVal, fooCompute) {\n \tfooCompute(+newVal);\n }\n});\n```\n","params":[{"types":[{"type":"String"}],"name":"converterName","description":"The name of the converter helper."},{"types":[{"type":"can-stache.getterSetter"}],"name":"getterSetter","description":"An object containing get() and set() functions.\n"}]}],"_curParam":{"types":[{"type":"can-stache.getterSetter"}],"name":"getterSetter","description":"An object containing get() and set() functions.\n"},"comment":" ","pathToRoot":".."}; </script> </article> <footer><p>CanJS is part of <a href="http://donejs.com" target="_blank">DoneJS</a>. 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