javascript - 在 JSON 对象中排序数组给出 TypeError : Cannot read property 'sort' of undefined

Question

我想在 javascript 中对一个对象进行排序。我有这个 json:

var unsorted = {
    "2014": [
        {
            "title": "Book",
            "value": 10
        },
        {
            "title": "Cheese",
            "value": 2
        }
    ],
    "2015": [
        {
            "title": "Movie",
            "value": 9
        }
    ],
     "2016": [
        {
            "title": "Slay",
            "value": 90
        },
        {
            "title": "Back",
            "value": 22
        }
    ],
    "selected_year": 2015
};

所以我想把这些年里面的jsons按照值进行排序。我试过这个:

var sorted = unsorted.items.sort(function(a, b) {return a.value - b.value});

alert.log(unsorted);
alert.log(sorted);

但问题是我有另一个字段不是 json "selected_year": 2015 并且它发出错误 TypeError: Cannot read property 'sort' of undefined

不知道怎么办？这是我的 JSFIDDLE

更新:我想对“年”内的数组进行排序，所以我得到了:

var sorted = {
        "2014": [
            {
              "title": "Cheese",
              "value": 2

            },
            {
              "title": "Book",
              "value": 10
            }
        ],
        "2015": [
            {
                "title": "Movie",
                "value": 9
            }
        ],
         "2016": [
             {
                 "title": "Back",
                 "value": 22
             },
            {
                "title": "Slay",
                "value": 90
            }

        ],
        "selected_year": 2015
    };

例如在排序后的“2014”里面我有:

"2014": [
        {
          "title": "Cheese",
          "value": 2

        },
        {
        "title": "Book",
        "value": 10
        }
    ]

Answer 1

您只能对数组属性进行排序:

var unsorted = {
    "2014": [
        {
            "title": "Book",
            "value": 10
        },
        {
            "title": "Cheese",
            "value": 2
        }
    ],
    "2015": [
        {
            "title": "Movie",
            "value": 9
        }
    ],
     "2016": [
        {
            "title": "Slay",
            "value": 90
        },
        {
            "title": "Back",
            "value": 22
        }
    ],
    "selected_year": 2015
};

var sorted = Object.assign({}, unsorted);  // Copy the unsorted object

Object.keys(sorted).forEach(key => {
  if (Array.isArray(sorted[key])) {
     sorted[key].sort((a, b) => a.value - b.value);
  }
})

console.log(sorted);