HTML syntax
Nue extends standard HTML with expressions, control flow, and components. Everything works on both server and client unless marked client-only.
Standard HTML
Every HTML document is a valid Nue document:
<!doctype html>
<html>
<head>...</head>
<body>
<article>
<button onclick="history.go(-1)">Back</button>
<button popovertarget="confirm-delete">Delete</button>
</article>
<dialog id="confirm-delete">
<h2>Delete user?</h2>
</dialog>
</body>
</html>Expressions
Insert dynamic values with curly brackets:
<!-- text content -->
<span>{ username }</span>
<!-- JavaScript expressions -->
<p>{ username.toUpperCase() }</p>
<!-- unescaped HTML -->
<div>{{ markdown(description) }}</div>
<div>{{ renderContent(article) }}</div>
<!-- triple brackets also supported -->
<div>{{{ userSubmittedContent }}}</div>
Attributes
Dynamic attributes use the same expression syntax:
<!-- attribute values -->
<time datetime="{ date.toISOString() }">
<!-- boolean attributes (falsy values remove the attribute) -->
<button disabled="{ is_disabled }">
<!-- class name interpolation -->
<div class="gallery { type }">
<!-- conditional classes -->
<div class="[ is-active: isActive, has-error: hasError ]">
<!-- combine static and dynamic -->
<div class="gallery { type } [ is-active: isActive ]">Loops
Render lists with :each:
<!-- basic loop -->
<li :each="item in items">{ item.name }</li>
<!-- with index -->
<li :each="item, i in items">
{ i }: { item.name }
</li>
<!-- destructuring -->
<li :each="{ name, price } in products">
{ name } costs { price }
</li>
<!-- loop objects -->
<li :each="[key, val] in Object.entries(data)">
{ key } = { val }
</li>
<!-- template loops (no wrapper element) -->
<dl>
<template :each="term in glossary">
<dt>{ term.word }</dt>
<dd>{ term.definition }</dd>
</template>
</dl>Conditionals
Control rendering with :if:
<p :if="count > 100">Too many!</p>
<p :else-if="count > 10">Getting there</p>
<p :else>{ count } items</p>
<!-- combine with loops (condition evaluated first) -->
<ul :if="items.length">
<li :each="item in items">{ item }</li>
</ul>
<p :else>No items</p>Components
Reusable pieces of UI:
<!-- define a component -->
<product-card>
<h3>{ name }</h3>
<p>{ price }</p>
<script>
// default values
this.name = 'Untitled'
this.price = 0
</script>
</product-card>
<!-- use the component -->
<product-card/>
<!-- pass properties -->
<product-card :name="Coffee" :price="12"/>
<!-- pass data variables -->
<product-card :name="productName" :price="productPrice"/>
<!-- shorthand (passes the name and price variables) -->
<product-card :name :price/>
<!-- regular attributes (no colon prefix) are rendered -->
<product-card id="featured" class="highlight"/>
<!-- loop components -->
<product-card :each="item in products" :bind="item"/>Component root element
Components default to <div> wrapper. Change with :is:
<!-- this component renders as <figure> -->
<figure :is="image-card">
<img src="{ url }">
<figcaption>{ caption }</figcaption>
</figure>Event handlers
Client-only - Handle user interactions:
<counter>
<button :onclick="count++">{ count }</button>
<script>
this.count = 0
</script>
</counter>
<!-- method handlers -->
<counter>
<button :onclick="increment">+</button>
<button :onclick="decrement">-</button>
<p>Count: { count }</p>
<p>Double: { double }</p>
<script>
this.count = 0
increment() {
this.count++
}
decrement() {
if (this.count > 0) this.count--
}
// getter methods are supported
get double() {
return this.count * 2
}
</script>
</counter>
<!-- event object -->
<form :onsubmit="handleSubmit">
<script>
handleSubmit(e) {
// forms automatically call e.preventDefault()
console.log('Submitted:', e.target)
}
</script>
</form>Lifecycle methods
Client-only - Run code at specific moments:
<user-profile>
<h2>{ user.name }</h2>
<script>
// before mounting to DOM
onmount() {
console.log('About to mount')
}
// after mounting to DOM
mounted() {
console.log('Mounted!')
}
// before updating
onupdate() {
console.log('About to update')
}
// after updating
updated() {
console.log('Updated!')
}
</script>
</user-profile>Manual updates
Client-only - Trigger component re-render with new data:
this.update(data)Event handlers update automatically, but async operations or external events (like web socket messages) need manual updates:
<script>
async mounted() {
const data = await fetch('/api/user')
const user = await data.json()
// Manual update required after async operations
this.update({ user })
}
</script>Dynamic mounting
Client-only - Mount components programmatically inside a single-page app:
this.mount(name, target, data)name - Component name
target - DOM element or CSS selector
data - Optional data to pass to component
<my-app>
<article/>
<script>
state.on('id', ({ id }) => {
this.mount(id ? 'user-details' : user-list', 'article')
})
</script>
</my-app>See single-page apps for routing patterns.
Shared scripts
Define functions and data for multiple components:
<!-- top-level script -->
<script>
// available to all components
const TAX_RATE = 0.08
function formatPrice(num) {
return '$' + num.toFixed(2)
}
</script>
<!-- use in components -->
<product-card>
<p>{ formatPrice(price) }</p>
<p>Tax: { formatPrice(price * TAX_RATE) }</p>
<script>
this.price = 10
</script>
</product-card>
<!-- another component definition -->
<shopping-cart>
<p>{ formatPrice(price) }</p>
<script>
// ...
</script<
</shopping-cart>JavaScript imports
Client-only - Import external modules:
<script>
import { formatDistance } from './utils.js'
import { store } from './store.js'
</script>
<!-- imported functions available in templates -->
<article>
<time>{ formatDistance(date) }</time>
<p>Cart items: { store.cart.length }</p>
</article>Passthrough scripts
Server-only - Scripts with type or src pass through unchanged:
<!-- these render as-is to the client -->
<script src="/analytics.js"></script>
<script type="module">
console.log('This runs on the client')
</script>Slots
Component composition pattern:
<!-- component with slot -->
<card>
<div class="card">
<slot/>
</div>
</card>
<!-- using the slot -->
<card>
<h2>This goes inside the card</h2>
<p>So does this</p>
</card>
<!-- multiple instances -->
<card :each="post in posts">
<h2>{ post.title }</h2>
<p>{ post.excerpt }</p>
</card>CSS variables
Pass design tokens without inline styles:
<!-- renders as style="--spacing: 2rem" -->
<section --spacing="2rem">
<style>
section {
padding: var(--spacing);
}
</style>
</section>
<!-- dynamic values -->
<div --columns="{ columnCount }">No inline styles or class overloading. Your design system stays the single source of truth.