Javascript 余烬找到关键元素的平均值

我试图通过选择一部电影的单独分数，并找到平均值来计算这个属性。这是有点棘手，但这是我到目前为止

testing: Ember.computed('movie.title', 'movie.rating', function() {
  return this.get('movie.title') + ', ' + this.get('movie.rating');
}),

averageScore: Ember.computed('review.@each.score', function() { //Used to determine each score of review
  return this.get('review').(function(sum, review) {
    return sum += review.get('score');
  }, 0) / this.get('reviews').get('length');
}),

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我知道我遗漏了什么，有什么建议吗？

sum

内置：

scores:       Ember.computed.mapBy('review', 'score'),
sumOfScores:  Ember.computed.sum('scores'),
averageScore: Ember.computed('sumOfScores', 'scores.length', function() {
  return this.get('sumOfScores') / this.get('scores.length');
}