javascript - JSON 文件中的动态 key (例如由 backbone.js 模型使用...)

Question

我正在尝试使用动态键创建一个 backbone.js 模型，但似乎无法正确完成。

这是我的模型:

window.MyModel = Backbone.Model.extend({
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: {
        "id": null,
        this.myDynamicVar : "USA",
        "country":  {
            "route":"test/test/test",
            "class":".usa2",
            "txt":"USA 2"
        },  
        "region":  "California",
        "year":  "",
        "description":  "",
        "picture":  ""
      }
});

在这里，我试图用我的模型中的内容替换 myDynamicVar。有没有想过我如何完成这项工作？提前致谢，吉米

Answer 1

您不能直接这样做；对象字面量中“:”的左边必须是常量。你可以做的是:

window.MyModel = Backbone.Model.extend({
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: function(fieldName) {
      var value = {
        "id": null,
        "country":  {
            "route":"test/test/test",
            "class":".usa2",
            "txt":"USA 2"
        },  
        "region":  "California",
        "year":  "",
        "description":  "",
        "picture":  ""
      };
      value[fieldName] = "USA";
      return value;
    }(this.myDynamicVar)
});

编辑 — 啊，我刚刚注意到“myDynamicVar”本身是外部对象的一部分。没有办法以这种方式用 this 引用它，所以如果那是你想要做的代码会有所不同:

window.MyModel = Backbone.Model.extend(function() {
  var value = {
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: {
        "id": null,
        "country":  {
            "route":"test/test/test",
            "class":".usa2",
            "txt":"USA 2"
        },  
        "region":  "California",
        "year":  "",
        "description":  "",
        "picture":  ""
      }
   };

   value.defaults.[value.myDynamicVar] = "USA";
   return value;
}());

如果您希望 myDynamicVar 自身 是动态的，那么您可以将其作为参数传入:

window.MyModel = Backbone.Model.extend(function(whichProperty) {
  var value = {
    myDynamicVar : "country",
    urlRoot: "api/myModel",
    defaults: {
        "id": null,
        "country":  {
            "route":"test/test/test",
            "class":".usa2",
            "txt":"USA 2"
        },  
        "region":  "California",
        "year":  "",
        "description":  "",
        "picture":  ""
      }
   };

   value.defaults.[value[whichProperty]] = "USA";
   return value;
}("myDynamicVar"));