MEAN STACK變量比較

Question

Specimen.find({ filter_fin : filter_spec }, 
    { 
     // Get only the taxonomy stuff 
     "taxonomy.phylum": 1, 
     "taxonomy.class": 1, 
     "taxonomy.order": 1, 
     "taxonomy.family": 1, 
     "taxonomy.genus": 1, 
     "taxonomy.species": 1, 
     "common_name": 1, 
     "last_edit": 1 
    }, 

以上是我的代碼，我的問題是，Specimen.find（{「taxonomy.class」：filter_spec}，它的工作原理。但是當把文本（「taxonomy.class」如果我不能做這個工作，將是非常低效的，因爲我必須使它處理幾個案例。

Answer 1

如果你想把對象在變量屬性，那麼你需要使用square bracket notation構造域對象如下：

var query = { }, 
    projection = { 
     // Get only the taxonomy stuff 
     "taxonomy.phylum": 1, 
     "taxonomy.class": 1, 
     "taxonomy.order": 1, 
     "taxonomy.family": 1, 
     "taxonomy.genus": 1, 
     "taxonomy.species": 1, 
     "common_name": 1, 
     "last_edit": 1 
    }; 

query[filter_fin] = filter_spec; 
Specimen.find(query, projection, callback); 

或者使用computed property names (ES6)：

var query = { 
     [filter_fin]: filter_spec 
    }, 
    projection = { 
     // Get only the taxonomy stuff 
     "taxonomy.phylum": 1, 
     "taxonomy.class": 1, 
     "taxonomy.order": 1, 
     "taxonomy.family": 1, 
     "taxonomy.genus": 1, 
     "taxonomy.species": 1, 
     "common_name": 1, 
     "last_edit": 1 
    }; 

Specimen.find(query, projection, callback);