实现一个虚拟dom，大概需要3个大的步骤：
- compile，把真实dom编译成vnode
- diff，oldNode和newVnode的变化
- patch，把变化用打补丁的方式更新到真实的dom
snabbdom也被用在了vue2中。
- Core features
- About 200 SLOC – you could easily read through the entire core and fully understand how it works.
- Extendable through modules.
- A rich set of hooks available, both per vnode and globally for modules, to hook into any part of the diff and patch process.
- Splendid performance. Snabbdom is among the fastest virtual DOM libraries.
- Patch function with a function signature equivalent to a reduce/scan function. Allows for easier integration with a FRP library.
- Features in modules
- h function for easily creating virtual DOM nodes.
- SVG just works with the h helper.
- Features for doing complex CSS animations.
- Powerful event listener functionality.
- Thunks to optimize the diff and patch process even further.
- Third party features
- JSX support thanks to snabbdom-pragma.
- Server-side HTML output provided by snabbdom-to-html.
- Compact virtual DOM creation with snabbdom-helpers.
- Template string support using snabby.
- Virtual DOM assertion with snabbdom-looks-like
