text: import { extend, cached, camelize } from 'shared/util'
  
  const normalize = cached(camelize)
  
  function createStyle (oldVnode, vnode) {
    if (!vnode.data.staticStyle) {
      updateStyle(oldVnode, vnode)
      return
    }
    const elm = vnode.elm
    const staticStyle = vnode.data.staticStyle
    const supportBatchUpdate = typeof elm.setStyles === 'function'
    const batchedStyles = {}
    for (const name in staticStyle) {
      if (staticStyle[name]) {
        supportBatchUpdate
          ? (batchedStyles[normalize(name)] = staticStyle[name])
          : elm.setStyle(normalize(name), staticStyle[name])
      }
    }
    if (supportBatchUpdate) {
      elm.setStyles(batchedStyles)
    }
    updateStyle(oldVnode, vnode)
  }
  
  function updateStyle (oldVnode, vnode) {
    if (!oldVnode.data.style && !vnode.data.style) {
      return
    }
    let cur, name
    const elm = vnode.elm
    const oldStyle = oldVnode.data.style || {}
    let style = vnode.data.style || {}
  
    const needClone = style.__ob__
  
    // handle array syntax
    if (Array.isArray(style)) {
      style = vnode.data.style = toObject(style)
    }
  
    // clone the style for future updates,
    // in case the user mutates the style object in-place.
    if (needClone) {
      style = vnode.data.style = extend({}, style)
    }
  
    const supportBatchUpdate = typeof elm.setStyles === 'function'
    const batchedStyles = {}
    for (name in oldStyle) {
      if (!style[name]) {
        supportBatchUpdate
          ? (batchedStyles[normalize(name)] = '')
          : elm.setStyle(normalize(name), '')
      }
    }
    for (name in style) {
      cur = style[name]
      supportBatchUpdate
        ? (batchedStyles[normalize(name)] = cur)
        : elm.setStyle(normalize(name), cur)
    }
    if (supportBatchUpdate) {
      elm.setStyles(batchedStyles)
    }
  }
  
  function toObject (arr) {
    const res = {}
    for (var i = 0; i < arr.length; i++) {
      if (arr[i]) {
        extend(res, arr[i])
      }
    }
    return res
  }
  
  export default {
    create: createStyle,
    update: updateStyle
  }
  