TypeError:无法读取未定义的属性“score”

Question

我知道有类似的问题，包括不能读取属性'分数'的未定义，但他们有<代码>如果（类型的结果[i 1]！='未定义'

var gamesArray = [
      { name: 'Edward', score: 21, rank: 0 },
      { name: 'Sharpe', score: 37, rank: 0 },
      { name: 'And', score: 45, rank: 0 },
      { name: 'The', score: 12, rank: 0 },
      { name: 'Magnetic', score: 3, rank: 0 },
      { name: 'Zeros', score: 37, rank: 0 }
    ];

    var sorted = gamesArray.sort(function(a,b){return b.score-a.score});
    // console.log (sorted);
    // [ { name: 'And', score: 45, rank: 0 },
    //   { name: 'Sharpe', score: 37, rank: 0 },
    //   { name: 'Zeros', score: 37, rank: 0 },
    //   { name: 'Edward', score: 21, rank: 0 },
    //   { name: 'The', score: 12, rank: 0 },
    //   { name: 'Magnetic', score: 3, rank: 0 } ]

    function rank(array) {

      var firstArray = array;
      var rankedArray = [];
      var counter = 0;

      while (firstArray.length > 0) { 

        //.shift removes the first slot of array and returns it
        var game = firstArray.shift();

        if (rankedArray.length == 0) {
          game.rank = 1;
          rankedArray.push(game);    
          game = null;
          counter += 1;

        } else {
          if (game.score == rankedArray[counter - 1].score) {
            game.rank = rankedArray[counter - 1].rank;
            counter += 1;
          } else {
            game.rank = rankedArray[counter - 1].rank + 1;
            counter += 1;
          };
        };

      };
      return rankedArray;
    };

    rank(gamesArray);

运行此命令时出现的错误是

   if (game.score == rankedArray[counter - 1].score) {
                                            ^
   TypeError: Cannot read property 'score' of undefined

Answer 1

循环1:和被推入rankedArray，排名1，计数器增长。

现在：firstArray。长度为5，rankedArray。长度为1，计数器为1

loop2:Sharpe正在使用秩2进行修改，不推动，计数器增长。

现在：第一个数组。长度是4，兰克达雷。长度为1，计数器为2

循环3：尝试访问rankedArray[计数器-1]。得分，现在等于rankedArray[1]。得分。但是rankedArray只包含一个元素。

SO：rankedArray[1]未定义，BOOM~~~

Answer 2

首先，不应该在循环中直接使用长度。

第二个错误是由于计数器增加，即使数组中只有第一个游戏推送：）

我假设它发生在第三次迭代中，在第一次迭代中，游戏被推到第二次，在第三次迭代中它被检查，它试图找到一些不存在的东西（索引1）

Answer 3

问题是，您只在第一次迭代时推动游戏。我已经在下面的代码中标记了移动的行。

var gamesArray = [
      { name: 'Edward', score: 21, rank: 0 },
      { name: 'Sharpe', score: 37, rank: 0 },
      { name: 'And', score: 45, rank: 0 },
      { name: 'The', score: 12, rank: 0 },
      { name: 'Magnetic', score: 3, rank: 0 },
      { name: 'Zeros', score: 37, rank: 0 }
    ];

    var sorted = gamesArray.sort(function(a,b){return b.score-a.score});
    // console.log (sorted);
    // [ { name: 'And', score: 45, rank: 0 },
    //   { name: 'Sharpe', score: 37, rank: 0 },
    //   { name: 'Zeros', score: 37, rank: 0 },
    //   { name: 'Edward', score: 21, rank: 0 },
    //   { name: 'The', score: 12, rank: 0 },
    //   { name: 'Magnetic', score: 3, rank: 0 } ]

    function rank(array) {

      var firstArray = array;
      var rankedArray = [];
      var counter = 0;

      while (firstArray.length > 0) { 

        //.shift removes the first slot of array and returns it
        var game = firstArray.shift();

        if (rankedArray.length == 0) {
          game.rank = 1;
          counter += 1;
        } else {
          if (game.score == rankedArray[counter - 1].score) {
            game.rank = rankedArray[counter - 1].rank;
            counter += 1;
          } else {
            game.rank = rankedArray[counter - 1].rank + 1;
            counter += 1;
          };
        };

        // Moved line
        rankedArray.push(game);
      };
      return rankedArray;
    };

    rank(gamesArray);