js/libs/ember-1.5.1.js
function(keyName, increment) {
    if (Ember.isNone(increment)) { increment = 1; }
    Ember.assert("Must pass a numeric value to incrementProperty", (!isNaN(parseFloat(increment)) && isFinite(increment)));
    set(this, keyName, (get(this, keyName) || 0) + increment);
    return get(this, keyName);
  }
function(keyName, increment) {
    if (Ember.isNone(increment)) { increment = 1; }
    Ember.assert("Must pass a numeric value to incrementProperty", (!isNaN(parseFloat(increment)) && isFinite(increment)));
    set(this, keyName, (get(this, keyName) || 0) + increment);
    return get(this, keyName);
  }
Set the value of a property to the current value plus some amount.

```javascript
person.incrementProperty('age');
team.incrementProperty('score', 2);
```

@method incrementProperty
@param {String} keyName The name of the property to increment
@param {Number} increment The amount to increment by. Defaults to 1
@return {Number} The new property value