yew/website/docs/concepts/html.md

title	sidebar_label	description
HTML	Introduction	The procedural macro for generating HTML and SVG

The html! macro allows you to write HTML and SVG code declaratively. It is similar to JSX an extension to JavaScript which allows you to write HTML-like code inside of JavaScript.

Important notes

1. The html! macro only accepts one root html node (you can counteract this by using fragments or iterators)
2. An empty html! {} invocation is valid and will not render anything
3. Literals must always be quoted and wrapped in braces: html! { "Hello, World" }

:::note The html! macro can reach the default recursion limit of the compiler. If you encounter compilation errors, add an attribute like #![recursion_limit="1024"] in the crate root to overcome the problem. :::

Tag Structure

Tags are based on HTML tags. Components, Elements, and Lists are all based on this tag syntax.

Tags must either self-close <... /> or have a corresponding end tag for each start tag.

html! {
  <div id="my_div"></div>
}

html! {
  <div id="my_div"> // <- MISSING CLOSE TAG
}

html! {
  <input id="my_input" />
}

html! {
  <input id="my_input"> // <- MISSING SELF-CLOSE
}

:::tip For convenience, elements which usually require a closing tag are allowed to self-close. For example, writing html! { <div class="placeholder" /> } is valid. :::

Children

Create complex nested HTML and SVG layouts with ease:

html! {
    <div>
        <div data-key="abc"></div>
        <div class="parent">
            <span class="child" value="anything"></span>
            <label for="first-name">{ "First Name" }</label>
            <input type="text" id="first-name" value="placeholder" />
            <input type="checkbox" checked=true />
            <textarea value="write a story" />
            <select name="status">
                <option selected=true disabled=false value="">{ "Selected" }</option>
                <option selected=false disabled=true value="">{ "Unselected" }</option>
            </select>
        </div>
    </div>
}

html! {
    <svg width="149" height="147" viewBox="0 0 149 147" fill="none" xmlns="http://www.w3.org/2000/svg">
        <path d="M60.5776 13.8268L51.8673 42.6431L77.7475 37.331L60.5776 13.8268Z" fill="#DEB819"/>
        <path d="M108.361 94.9937L138.708 90.686L115.342 69.8642" stroke="black" stroke-width="4" stroke-linecap="round" stroke-linejoin="round"/>
        <g filter="url(#filter0_d)">
            <circle cx="75.3326" cy="73.4918" r="55" fill="#FDD630"/>
            <circle cx="75.3326" cy="73.4918" r="52.5" stroke="black" stroke-width="5"/>
        </g>
        <circle cx="71" cy="99" r="5" fill="white" fill-opacity="0.75" stroke="black" stroke-width="3"/>
        <defs>
            <filter id="filter0_d" x="16.3326" y="18.4918" width="118" height="118" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">
                <feGaussianBlur stdDeviation="2"/>
                <feColorMatrix in="SourceAlpha" type="matrix" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 127 0"/>
            </filter>
        </defs>
    </svg>
}

Special properties

There are special properties which don't directly influence the DOM but instead act as instructions to Yew's virtual DOM. Currently, there are two such special props: ref and key.

ref allows you to access and manipulate the underlying DOM node directly. See Refs for more details.

key on the other hand gives an element a unique identifier which Yew can use for optimization purposes.

:::important The documentation for keys is yet to be written. See #1263.

For now, use keys when you have a list where the order of elements changes. This includes inserting or removing elements from anywhere but the end of the list. :::