attr.js

// xlink
var xlinkNS = 'http://www.w3.org/1999/xlink'
var xlinkRE = /^xlink:/

module.exports = {

  priority: 850,

  update: function (value) {
    if (this.arg) {
      this.setAttr(this.arg, value)
    } else if (typeof value === 'object') {
      this.objectHandler(value)
    }
  },

  objectHandler: function (value) {
    // cache object attrs so that only changed attrs
    // are actually updated.
    var cache = this.cache || (this.cache = {})
    var attr, val
    for (attr in cache) {
      if (!(attr in value)) {
        this.setAttr(attr, null)
        delete cache[attr]
      }
    }
    for (attr in value) {
      val = value[attr]
      if (val !== cache[attr]) {
        cache[attr] = val
        this.setAttr(attr, val)
      }
    }
  },

  setAttr: function (attr, value) {
    if (value || value === 0) {
      if (xlinkRE.test(attr)) {
        this.el.setAttributeNS(xlinkNS, attr, value)
      } else {
        this.el.setAttribute(attr, value)
      }
    } else {
      this.el.removeAttribute(attr)
    }
  }

}