mithril
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A framework for building brilliant applications
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<h1><img src="logo.svg"> Mithril <small>1.0.0</small></h1>
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<h1 id="the-auto-redraw-system">The auto-redraw system</h1>
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<li>Tutorials<ul>
<li><a href="installation.html">Installation</a></li>
<li><a href="index.html">Introduction</a></li>
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<li>Key concepts<ul>
<li><a href="vnodes.html">Vnodes</a></li>
<li><a href="components.html">Components</a></li>
<li><a href="lifecycle-methods.html">Lifecycle methods</a></li>
<li><a href="keys.html">Keys</a></li>
<li><strong><a href="autoredraw.html">Autoredraw system</a></strong></li>
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<p>Mithril implements a virtual DOM diffing system for fast rendering, and in addition, it offers various mechanisms to gain granular control over the rendering of an application.</p>
<p>When used idiomatically, Mithril employs an auto-redraw system that synchronizes the DOM whenever changes are made in the data layer. The auto-redraw system becomes enabled when you call <code>m.mount</code> or <code>m.route</code> (but it stays disabled if your app is bootstrapped solely via <code>m.render</code> calls).</p>
<p>The auto-redraw system simply consists of triggering a re-render function behind the scenes after certain functions complete.</p>
<h3 id="after-event-handlers">After event handlers</h3>
<p>Mithril automatically redraws after DOM event handlers that are defined in a Mithril view:</p>
<pre><code class="lang-javascript">var MyComponent = {
view: function() {
return m("div", {onclick: doSomething})
}
}
function doSomething() {
// a redraw happens synchronously after this function runs
}
m.mount(document.body, MyComponent)
</code></pre>
<p>You can disable an auto-redraw for specific events by setting <code>e.redraw</code> to <code>false</code>.</p>
<pre><code class="lang-javascript">var MyComponent = {
view: function() {
return m("div", {onclick: doSomething})
}
}
function doSomething(e) {
e.redraw = false
// no longer triggers a redraw when the div is clicked
}
m.mount(document.body, MyComponent)
</code></pre>
<h3 id="after-mrequest">After m.request</h3>
<p>Mithril automatically redraws after <a href="request.html"><code>m.request</code></a> completes:</p>
<pre><code class="lang-javascript">m.request("/api/v1/users").then(function() {
// a redraw happens after this function runs
})
</code></pre>
<p>You can disable an auto-redraw for a specific request by setting the <code>background</code> option to true:</p>
<pre><code class="lang-javascript">m.request("/api/v1/users", {background: true}).then(function() {
// does not trigger a redraw
})
</code></pre>
<h3 id="after-route-changes">After route changes</h3>
<p>Mithril automatically redraws after <a href="route.html#mrouteset"><code>m.route.set()</code></a> calls (or route changes via links that use <a href="route.html#mroutelink"><code>m.route.link</code></a></p>
<pre><code class="lang-javascript">var RoutedComponent = {
view: function() {
return [
// a redraw happens asynchronously after the route changes
m("a", {href: "/", oncreate: m.route.link}),
m("div", {
onclick: function() {
m.route.set("/")
}
}),
]
}
}
m.route(document.body, "/", {
"/": RoutedComponent,
})
</code></pre>
<hr>
<h3 id="when-mithril-does-not-redraw">When Mithril does not redraw</h3>
<p>Mithril does not redraw after <code>setTimeout</code>, <code>setInterval</code>, <code>requestAnimationFrame</code>, raw <code>Promise</code> resolutions and 3rd party library event handlers (e.g. Socket.io callbacks). In those cases, you must manually call <a href="redraw.html"><code>m.redraw()</code></a>.</p>
<p>Mithril also does not redraw after lifecycle methods. Parts of the UI may be redrawn after an <code>oninit</code> handler, but other parts of the UI may already have been redrawn when a given <code>oninit</code> handler fires. Handlers like <code>oncreate</code> and <code>onupdate</code> fire after the UI has been redrawn.</p>
<p>If you need to explicitly trigger a redraw within a lifecycle method, you should call <code>m.redraw()</code>, which will trigger an asynchronous redraw.</p>
<pre><code class="lang-javascript">var StableComponent = {
oncreate: function(vnode) {
vnode.state.height = vnode.dom.offsetHeight
m.redraw()
},
view: function() {
return m("div", "This component is " + vnode.state.height + "px tall")
}
}
</code></pre>
<p>Mithril does not auto-redraw vnode trees that are rendered via <code>m.render</code>. This means redraws do not occur after event changes and <code>m.request</code> calls for templates that were rendered via <code>m.render</code>. Thus, if your architecture requires manual control over when rendering occurs (as can sometimes be the case when using libraries like Redux), you should use <code>m.render</code> instead of <code>m.mount</code>.</p>
<p>Remember that <code>m.render</code> expects a vnode tree, and <code>m.mount</code> expects a component:</p>
<pre><code class="lang-javascript">// wrap the component in a m() call for m.render
m.render(document.body, m(MyComponent))
// don't wrap the component for m.mount
m.mount(document.body, MyComponent)
</code></pre>
<p>Mithril may also avoid auto-redrawing if the frequency of requested redraws is higher than one animation frame (typically around 16ms). This means, for example, that when using fast-firing events like <code>onresize</code> or <code>onscroll</code>, Mithril will automatically throttle the number of redraws to avoid lag.</p>
<hr />
<small>License: MIT. © Leo Horie.</small>
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