前言

中文API：http://www.css88.com/doc/zeptojs_api
Zepto是一个小巧的dom操作库，非常适合研究源码。如果想不依赖此库的话，可以直接用里面的代码或查看以下文章：
http://www.ruanyifeng.com/blog/2013/05/jquery-free.html

结构

Paste_Image.png

整个库是一个Immediately-Invoked Function Expression (IIFE)，核心部分是Zepto，主要包含dom树操作，到945行算结束了，之后是其他模块的初始化。

入口

所有功能即调用zepto.init

    // `$` will be the base `Zepto` object. When calling this
    // function just call `$.zepto.init, which makes the implementation
    // details of selecting nodes and creating Zepto collections
    // patchable in plugins.
    $ = function(selector, context){
      return zepto.init(selector, context)
    }

最后返回给Zepto就是这个$

    // Export internal API functions in the `$.zepto` namespace
    zepto.uniq = uniq
    zepto.deserializeValue = deserializeValue
    $.zepto = zepto

    return $```
##zepto.init
根据select的不同而更分发到不同的功能。主要包含字符串（css选择器）、function（文档加载时执行）和Z（Zepto模块）

// `$.zepto.init` is Zepto's counterpart to jQuery's `$.fn.init` and
// takes a CSS selector and an optional context (and handles various
// special cases).
// This method can be overridden in plugins.
zepto.init = function(selector, context) {
  var dom
  // If nothing given, return an empty Zepto collection
  if (!selector) return zepto.Z()
  // Optimize for string selectors
  else if (typeof selector == 'string') {
    selector = selector.trim()
    // If it's a html fragment, create nodes from it
    // Note: In both Chrome 21 and Firefox 15, DOM error 12
    // is thrown if the fragment doesn't begin with <
    if (selector[0] == '<' && fragmentRE.test(selector))
      dom = zepto.fragment(selector, RegExp.$1, context), selector = null
    // If there's a context, create a collection on that context first, and select
    // nodes from there
    else if (context !== undefined) return $(context).find(selector)
    // If it's a CSS selector, use it to select nodes.
    else dom = zepto.qsa(document, selector)
  }
  // If a function is given, call it when the DOM is ready
  else if (isFunction(selector)) return $(document).ready(selector)
  // If a Zepto collection is given, just return it
  else if (zepto.isZ(selector)) return selector
  else {
    // normalize array if an array of nodes is given
    if (isArray(selector)) dom = compact(selector)
    // Wrap DOM nodes.
    else if (isObject(selector))
      dom = [selector], selector = null
    // If it's a html fragment, create nodes from it
    else if (fragmentRE.test(selector))
      dom = zepto.fragment(selector.trim(), RegExp.$1, context), selector = null
    // If there's a context, create a collection on that context first, and select
    // nodes from there
    else if (context !== undefined) return $(context).find(selector)
    // And last but no least, if it's a CSS selector, use it to select nodes.
    else dom = zepto.qsa(document, selector)
  }
  // create a new Zepto collection from the nodes found
  return zepto.Z(dom, selector)
}

剩余部分为add、css、remove等dom操作的封装。