function Attribute(name, index){
  this.name = name;
  this.basevalue = 10;
  this.bonus = 0;
  this.index = index;
};

Attribute.prototype = {
  getValue: function () { return this.basevalue + this.bonus; }
  getMod: function () { return parseInt((this.getValue() - 10)/2); }
}

<tr ng-repeat="attribute in character.attributes">
  <td>{{attribute.name | uppercase}}
  <td>{{attribute.getValue()}}
  <td>{{attribute.getMod()}}
  <td>{{attribute.basevalue}}
  <td><input type="number" ng-model="attribute.bonus">
</tr>