SVG.extend(SVG.Element, {
  // Store data values on svg nodes
  data: function(a, v, r) {
    if (typeof a == 'object') {
      for (v in a)
        this.data(v, a[v])

    } else if (arguments.length < 2) {
      try {
        return JSON.parse(this.attr('data-' + a))
      } catch(e) {
        return this.attr('data-' + a)
      }
      
    } else {
      this.attr(
        'data-' + a
      , v === null ?
          null :
        r === true || typeof v === 'string' || typeof v === 'number' ?
          v :
          JSON.stringify(v)
      )
    }
    
    return this
  }
})