src/data.js

//     Zepto.js
//     (c) 2010-2016 Thomas Fuchs
//     Zepto.js may be freely distributed under the MIT license.

// The following code is heavily inspired by jQuery's $.fn.data()

;(function($){
  var data = {}, dataAttr = $.fn.data, camelize = $.camelCase,
    exp = $.expando = 'Zepto' + (+new Date()), emptyArray = []

  // Get value from node:
  // 1. first try key as given,
  // 2. then try camelized key,
  // 3. fall back to reading "data-*" attribute.
  function getData(node, name) {
    var id = node[exp], store = id && data[id]
    if (name === undefined) return store || setData(node)
    else {
      if (store) {
        if (name in store) return store[name]
        var camelName = camelize(name)
        if (camelName in store) return store[camelName]
      }
      return dataAttr.call($(node), name)
    }
  }

  // Store value under camelized key on node
  function setData(node, name, value) {
    var id = node[exp] || (node[exp] = ++$.uuid),
      store = data[id] || (data[id] = attributeData(node))
    if (name !== undefined) store[camelize(name)] = value
    return store
  }

  // Read all "data-*" attributes from a node
  function attributeData(node) {
    var store = {}
    $.each(node.attributes || emptyArray, function(i, attr){
      if (attr.name.indexOf('data-') == 0)
        store[camelize(attr.name.replace('data-', ''))] =
          $.zepto.deserializeValue(attr.value)
    })
    return store
  }

  $.fn.data = function(name, value) {
    return value === undefined ?
      // set multiple values via object
      $.isPlainObject(name) ?
        this.each(function(i, node){
          $.each(name, function(key, value){ setData(node, key, value) })
        }) :
        // get value from first element
        (0 in this ? getData(this[0], name) : undefined) :
      // set value on all elements
      this.each(function(){ setData(this, name, value) })
  }

  $.data = function(elem, name, value) {
    return $(elem).data(name, value)
  }

  $.hasData = function(elem) {
    var id = elem[exp], store = id && data[id]
    return store ? !$.isEmptyObject(store) : false
  }

  $.fn.removeData = function(names) {
    if (typeof names == 'string') names = names.split(/\s+/)
    return this.each(function(){
      var id = this[exp], store = id && data[id]
      if (store) $.each(names || store, function(key){
        delete store[names ? camelize(this) : key]
      })
    })
  }

  // Generate extended `remove` and `empty` functions
  ;['remove', 'empty'].forEach(function(methodName){
    var origFn = $.fn[methodName]
    $.fn[methodName] = function() {
      var elements = this.find('*')
      if (methodName === 'remove') elements = elements.add(this)
      elements.removeData()
      return origFn.call(this)
    }
  })
})(Zepto)