htm
is JSX-like syntax in plain JavaScript - no transpiler necessary.
Develop with React/Preact directly in the browser, then compile htm
away for production.
It's built using Tagged Templates and the browser's HTML parser.
๐ฃ 700 bytes when used directly in the browser
โ๏ธ 500 bytes when used with Preact (thanks gzip ๐)
๐ 0 bytes when compiled using babel-plugin-htm
The syntax is inspired by lit-html, but includes features familiar to anyone who works with JSX:
- Rest spread:
<div ...${props}>
- Self-closing tags:
<div />
- Components:
<${Foo}>
(whereFoo
is a component reference) - Boolean attributes:
<div draggable />
htm
actually takes the JSX-style syntax a couple steps further!
Here's some ergonomic features you get for free that aren't present in JSX:
- No transpiler necessary
- HTML's optional quotes:
<div class=foo>
- HTML's self-closing tags:
<img src=${url}>
- Optional end-tags:
<section><h1>this is the whole template!
- Component end-tags:
<${Footer}>footer content<//>
- Support for HTML comments:
<div><!-- don't delete this! --></div>
- Syntax highlighting and language support via the lit-html VSCode extension.
The original goal for htm
was to create a wrapper around Preact that felt natural for use untranspiled in the browser. I wanted to use Virtual DOM, but I wanted to eschew build tooling and use ES Modules directly.
This meant giving up JSX, and the closest alternative was Tagged Templates. So, I wrote this library to patch up the differences between the two as much as possible. As it turns out, the technique is framework-agnostic, so it should work great with most Virtual DOM libraries.
htm
is published to npm, and accessible via the unpkg.com CDN:
via npm:
npm i htm
hotlinking from unpkg: (no build tool needed!)
import htm from 'https://unpkg.com/htm?module'
const html = htm.bind(React.createElement);
// just want htm + preact in a single file? there's a highly-optimized version of that:
import { html, render } from 'https://unpkg.com/htm/preact/standalone.mjs'
Since htm
is a generic library, we need to tell it what to "compile" our templates to.
The target should be a function of the form h(tag, props, ...children)
(hyperscript), and can return anything.
// this is our hyperscript function. for now, it just returns an description object.
function h(tag, props, ...children) {
return { tag, props, children };
}
To use that h()
function, we need to create our own html
tag function by binding htm
to our h()
function:
import htm from 'htm';
const html = htm.bind(h);
Now we have an html()
template tag that can be used to produce objects in the format we created above.
Here's the whole thing for clarity:
import htm from 'htm';
function h(tag, props, ...children) {
return { tag, props, children };
}
const html = htm.bind(h);
console.log( html`<h1 id=hello>Hello world!</h1>` );
// {
// tag: 'h1',
// props: { id: 'hello' },
// children: ['Hello world!']
// }
Curious to see what it all looks like? Here's a working app!
It's a single HTML file, and there's no build or tooling. You can edit it with nano.
<!DOCTYPE html>
<html lang="en">
<title>htm Demo</title>
<script type="module">
import { html, Component, render } from 'https://unpkg.com/htm/preact/standalone.mjs';
class App extends Component {
addTodo() {
const { todos = [] } = this.state;
this.setState({ todos: todos.concat(`Item ${todos.length}`) });
}
render({ page }, { todos = [] }) {
return html`
<div class="app">
<${Header} name="ToDo's (${page})" />
<ul>
${todos.map(todo => html`
<li>${todo}</li>
`)}
</ul>
<button onClick=${() => this.addTodo()}>Add Todo</button>
<${Footer}>footer content here<//>
</div>
`;
}
}
const Header = ({ name }) => html`<h1>${name} List</h1>`
const Footer = props => html`<footer ...${props} />`
render(html`<${App} page="All" />`, document.body);
</script>
</html>
Here's a live version.
How nifty is that? Notice there's only one import - here we're using the prebuilt Preact integration since it's easier to import and a bit smaller.
The same example works fine without the prebuilt version, just using two imports:
import { h, Component, render } from 'preact';
import htm from 'htm';
const html = htm.bind(h);
render(html`<${App} page="All" />`, document.body);
Since htm
is designed to meet the same need as JSX, you can use it anywhere you'd use JSX.
Generate HTML using vhtml:
import htm from 'htm';
import vhtml from 'vhtml';
const html = htm.bind(vhtml);
console.log( html`<h1 id=hello>Hello world!</h1>` );
// '<h1 id="hello">Hello world!</h1>'
Webpack configuration via jsxobj: (details here)
import htm from 'htm';
import jsxobj from 'jsxobj';
const html = htm.bind(jsxobj);
console.log(html`
<webpack watch mode=production>
<entry path="src/index.js" />
</webpack>
`);
// {
// watch: true,
// mode: 'production',
// entry: {
// path: 'src/index.js'
// }
// }