Astro Syntax

code fence: ---

dynamics is in code fence reactive is not

{local variable} ${local variable}

<MyComponent templateLiteralNameAttribute={`MyNameIs${name}`} />

HTML attributes will be converted to strings

<!-- ❌ This doesn't work! ❌ -->
<button onClick={handleClick}>click me!</button>

Instead, use a client-side script to add the event handler, like you would in vanilla JavaScript:

<button id="button">Click Me</button>
<script>
  function handleClick () {
    console.log("button clicked!");
  }
  document.getElementById("button").addEventListener("click", handleClick);
</script>

Local variables can be used in JSX-like functions to produce dynamically-generated HTML elements:

const items = [“Dog”, “Cat”, “Platypus”];

{items.map((item) => (
• {item}
))}

Astro can conditionally display HTML using JSX logical operators and ternary expressions.

const visible = true;

{visible &&

Show me!

{visible ?

Show me!

Else show me!

### Dynamic Tags

import MyComponent from “./MyComponent.astro”; const Element = ‘div’ const Component = MyComponent;

Hello!

When using dynamic tags:

- **Variable names must be capitalized.** For example, use `Element`, not `element`. Otherwise, Astro will try to render your variable name as a literal HTML tag.

- **Hydration directives are not supported.** When using [`client:*` hydration directives](/en/core-concepts/framework-components/#hydrating-interactive-components), Astro needs to know which components to bundle for production, and the dynamic tag pattern prevents this from working.

### Fragments

Astro supports using either `<Fragment> </Fragment>` or the shorthand `<> </>`.

Fragments can be useful to avoid wrapper elements when adding [`set:*` directives](/en/reference/directives-reference/#sethtml), as in the following example:

```astro title="src/components/SetHtml.astro" "Fragment"
---
const htmlString = '<p>Raw HTML content</p>';
---
<Fragment set:html={htmlString} />

Differences between Astro and JSX

Astro component syntax is a superset of HTML. It was designed to feel familiar to anyone with HTML or JSX experience, but there are a couple of key differences between .astro files and JSX.

Attributes

In Astro, you use the standard kebab-case format for all HTML attributes instead of the camelCase used in JSX. This even works for class, which is not supported by React.

Multiple Elements

An Astro component template can render multiple elements with no need to wrap everything in a single <div> or <>, unlike JavaScript or JSX.

---
// Template with multiple elements
---
<p>No need to wrap elements in a single containing element.</p>
<p>Astro supports multiple root elements in a template.</p>