A Fast & Light Virtual DOM Alternative - release post, now available for both client, server and also simplified for Custom Elements.

New Experimental .adopt(node) API

Since version 0.12 you can hyperHTML.adopt(node) instead of hyperHTML.bind(node) in case you have already rendered a node on the server via viperHTML and you are sharing the same template.

Adopting a node will not trash the node content, it will map it to the existent one.

Don't miss the viperHTML version of Hacker News

Live: https://viperhtml-164315.appspot.com/

Repo: https://github.com/WebReflection/viper-news

There are two basic but fundamental rules to remember:

1. attributes, as well as eventual callbacks, must be defined inside single or double quoted attributes
2. if there's any char different from > and < surrounding the interpolation, that content will be text, instead of HTML

Please read the Getting Started for more examples.

The easiest way to describe hyperHTML is through an example.

// this is React's first tick example
// https://facebook.github.io/react/docs/state-and-lifecycle.html
function tick() {
  const element = (
    <div>
      <h1>Hello, world!</h1>
      <h2>It is {new Date().toLocaleTimeString()}.</h2>
    </div>
  );
  ReactDOM.render(
    element,
    document.getElementById('root')
  );
}
setInterval(tick, 1000);

// this is hyperHTML
function tick(render) {
  render`
    <div>
      <h1>Hello, world!</h1>
      <h2>It is ${new Date().toLocaleTimeString()}.</h2>
    </div>
  `;
}
setInterval(tick, 1000,
  hyperHTML.bind(document.getElementById('root'))
);

• every modern browser (Chrome, Edge, Firefox, Safari)
• IE9 to IE11 on both Mobile and Desktop
• every other Mobile or Desktop browser compatible with Babel transpilation

• Zero dependencies and it fits in less than 3KB (minzipped)
• Uses directly native DOM instead of inventing new syntax/APIs, DOM diffing, or virtual DOM
• Designed for template literals, a templating feature built in to JS
• Compatible with vanilla DOM elements and vanilla JS data structures *
• Also compatible with Babel transpiled output, hence suitable for every browser you can think of

* ^{_{actually, this is just a 100% vanilla JS utility, that's why is most likely the fastest and also the smallest. I also feel like I'm writing Assembly these days ... anyway ...}}

You have a hyperHTML function that is suitable for parsing template literals but it needs a DOM node context to operate.

If you want to render many times the same template for a specific node, bind it once and boost up performance for free. No new nodes, or innerHTML, will be ever used in such case: safe listeners, faster DOM.

You can also check the TodoMVC repository or its live demo.

The helper hyperHTML.wire([obj[, type]]) is the solution to a common use case: using hyperHTML to define not the content of a node, but the node itself, or a list of nodes.

In this case binding a DocumentFragment would work but it will also lose its content as soon as it's appended. Using hyperHTML.wire(obj) will grant that render will always work as expected, without ever losing knowledge of its initial content.

It wires render updates to whatever content is holding.

// hyperHTML.wire() returns a new wire
const render = hyperHTML.wire();
// which can be used multiple times
const update = () => render`
  <div>Hello Wired!</div>
`;

update() === update(); // true
update(); // <div>Hello Wired!</div>

// it is possible to reference a wire
const point = {x: 1, y: 2};
// simply passing a generic object
hyperHTML.wire(point)`
  <span style="${`
    position: absolute;
    left: ${point.x}px;
    top: ${point.y}px;
  `}">O</span>
`;

// the used render will be always the same
hyperHTML.wire(point) === hyperHTML.wire(point);
// true

It is also possible to define a generic template, and in such case the update won't be the single node, but an Array of nodes.

Following example illustrates a common usecase for wire:

const root = document.getElementById('root');

// We want to get a li element, without caring about any root
const Item = (item) => hyperHTML.wire(item)`
  <li>Lib: ${item.name}, size: ${item.value}</li>
`

const UnorderedList = ({ root, items }) => root`
  <ul>${
    items.map(Item)
  }</ul>
`

const OrderedList = ({ root, items }) => root`
  <ol>${
    items.map(Item)
  }</ol>
`

UnorderedList({
  root: hyperHTML.bind(root.appendChild(document.createElement('div'))),
  items: [
    { name: 'hyperHTML', value: '5KB' },
    { name: 'document-register-element polyfill', value: '12KB' },
    { name: 'app', value: '20KB' }
  ]
})

OrderedList({
  root: hyperHTML.bind(root.appendChild(document.createElement('div'))),
  items: [
    { name: 'hyperHTML', value: '5KB' },
    { name: 'vue', value: '25KB' },
    { name: 'others', value: '...' }
  ]
})

We can see that Item is used to render li element, without root or its parent element.

An object can have multiple wires associated with it using different :ids as type.

// item used to render an option
hyperHTML.wire(obj, ':option')`
  <option value="${obj.value}"> ${obj.choice} </option>`;


// same item used to render an li
hyperHTML.wire(obj, ':li')`
  <li> ${obj.content} </li>`;

It is still possible to specify a type using svg:id or html:id.

• will input lose focus? Nope, as you can test, only what needs to be updated will be updated.

• are events stringified? Nope, even if visually set as <a onclick="${help.click}"> events are treated differently from other attributes. That help.click will be indeed directly assigned as a.onclick = help.click so don't worry 😉

• how can I differentiate between textContent only and HTML or DOM nodes? If there's any space or char around the value, that'd be a textContent. Otherwise it can be strings, used as html, or DOM nodes. As summary: render`<p>This is: ${'text'}</p>`; for text, and render`<p>${'html' || node || array}</p>`; for other cases. An array will result into html, if its content has strings, or a document fragment, if it contains nodes. I've thought a pinch of extra handy magic would've been nice there 😉.

• can I use different renders for a single node? Sure thing. However, the best performance gain is reached with nodes that always use the same template string. If you have a very unpredictable conditional template, you might want to create two different nodes and apply hyperHTML with the same template for both of them, swapping them when necessary. In every other case, the new template will create new content and map it once per change.

• is this project just the same as yo-yo or bel ? First of all, I didn't even know those projects were existing when I've written hyperHTML, and while the goal is quite similar, the implementation is very different. For instance, hyperHTML performance seems to be superior than yo-yo-perf. You can directly test hyperHTML DBMonster benchmark and see it goes N times faster than yo-yo version on both Desktop and Mobile browsers 🎉.

For all other deeper dirty details, please check the DeepDive page.

ES6 Template literals come with a special feature that is not commonly used: prefixed transformers.

Using such feature to map a template string to a generic DOM node, makes it possible to automatically target and update only the differences between two template invokes and with no innerHTML involved.

Following an example:

function update(render, state) {
  render`
  <article data-magic="${state.magic}">
    <h3> ${state.title} </h3>
    List of ${state.paragraphs.length} paragraphs:
    <ul>${
      // if you want to create wired node instead
      // .map(p => hyperHTML.wire(p)`<li>${p.title}</li>`)
      // otherwise it will be just injected as array of strings
      // without any special power, simply generated via literals
      state.paragraphs
        .map(p => `<li>${p.title}</li>`)
    }</ul>
  </article>
  `;
}

update(
  hyperHTML.bind(articleElement),
  {
    title: 'True story',
    magic: true,
    paragraphs: [
      {title: 'touching'},
      {title: 'incredible'},
      {title: 'doge'}
    ]
  }
);

Since most of the time templates are 70% static text and 30% or less dynamic, hyperHTML passes through the resulting string only once, finds all attributes and content that is dynamic, and maps it 1:1 to the node to make updates as cheap as possible for both node attributes and node content.

Following a list of hyperHTML caveats.

To achieve best performance at setup time, a special <!-- comment --> is used the first time as template values.

This makes it possible to quickly walk through the DOM tree and setup behaviors, but it's also the value looked for within attributes.

Unfortunately, if you have html such <div attr=<!-- comment --> class="any"></div> the result is broken, while using single or double quotes will grant a successful operation. This is the biggest, and so far only, real caveat.

In summary, always write <p attr="${'OK'}"></p> instead of <p attr=${'OK'}></p>, or the layout will break, even if the attribute is a number or a boolean.

In this way you'll also ensure whatever value you'll pass later on won't ever break the layout. It's a bit annoying, yet a win.

Attributes like image src or srcset might involve failing network requests or some overly-scary console error even if nothing would be really compromised.

This is caused by the fact hyperHTML uses a place holder for all attributes but some browser might try to load such string even if not a valid URL.

Eventually, this console warning would happen only once per container or wire, but you can always augment network sensible attributes in two steps.

const srcset = ["foo.png 200w"];

// use this update
function withSrcset(srcset, alt) {
  var img = toImage(alt);
  img.srcset = srcset.join(" ");
  return img;
}

// instead of just this one
function toImage(alt) {
  return hyperHTML.wire()
  `<img
      role="button"
      alt="${alt}"
      width="195" height="80"/>`;
}

If your string literals are transpiled, this project should be compatible with every single browser, old or new.

If you don't transpile string literals, check the test page and wait 'till it's green.