Question

当我运行非常简单的以下代码时，出于某种原因，我在浏览器控制台中得到以下结果：＆＃34; 6您还没有看过undefined undefined。＆＃34;有人能指出我的错误吗？

＆＃13;

datalab: command not found

＆＃13;

Answer 1

您有一个对象数组，因此您需要引用每个数组元素的索引。您还需要将循环减少一个，因为数组索引从零开始，但长度不是。

var movies = [{
    title: "The Mummy",
    hasWatched: true,
    stars: "5 stars"
  },

  {
    title: "About A Boy",
    hasWatched: true,
    stars: "5 stars"
  },


  {
    title: "It",
    hasWatched: false,
    stars: "5 stars"
  },


  {
    title: "Cleopatra",
    hasWatched: false,
    stars: "5 stars"
  }

];

for (var i = 0; i < movies.length; i++) {
  if (movies[i].hasWatched) {
    console.log("You have watched " + movies[i].title + " " + movies[i].stars + ".");
  } else {
    console.log("You have not watched " + movies[i].title + " " + movies[i].stars + ".");
  }

}

Answer 2

将for条件更改为i < movies.length;你有一个额外的迭代。您还需要引用movies[i]来获取实际的电影，例如movies[i].title。

在上面的示例中，最后一个索引是3（项目编号为0,1,2,3），但是您的循环将一直运行到4并且将尝试查找movies[4].title并返回undefined。

Answer 3

for (var i = 0; i <= movies.length; i++) {
  if (movies[i].hasWatched) {
    console.log("You have watched " + movies[i].title + " " + movies[i].stars + ".");
 } else {
    console.log("You have not watched " + movies[i].title + " " + movies[i].stars + ".");
  }

}

您在访问

时只是缺少索引标识符

＆＃39;对于＆＃39;循环没有正确循环通过对象数组

3 个答案: