d3 attr修改源碼支持object輸入

function selection_attr(name, value) {
  var fullname = namespace(name);

  if (arguments.length < 2) {
    // TODO:
    if (typeof(arguments[0]) === 'object') {
      for(var item in arguments[0]) {
        var key = namespace(item);
        var todo = arguments[0][item];
        this.each((todo == null
          ? (key.local ? attrRemoveNS : attrRemove) : (typeof todo === "function"
          ? (key.local ? attrFunctionNS : attrFunction)
          : (key.local ? attrConstantNS : attrConstant)))(key, todo));
      }
      return this
      // end TODO:
    } else {
      var node = this.node();
      return fullname.local
          ? node.getAttributeNS(fullname.space, fullname.local)
          : node.getAttribute(fullname);
    }
  }

  return this.each((value == null
      ? (fullname.local ? attrRemoveNS : attrRemove) : (typeof value === "function"
      ? (fullname.local ? attrFunctionNS : attrFunction)
      : (fullname.local ? attrConstantNS : attrConstant)))(fullname, value));
}