Javascript对象返回未定义

Question

var movies = 
[
{name: "In Bruges", rating:"4.7", seen:false},
{name: "Frozen", rating: "4.5", seen:true},
{name: "Lion King", rating:"5", seen:true},
]


for (var i = 0; i < movies.length; i++) {
    var result = "You have ";
    if(movies.seen === true){
        result += "watched ";
    }
    else{
        result += "not seen ";
    }
    result += "\"" + movies.name + "\" - ";
    result += movies.rating + " stars"
    console.log(result)
};

You have not seen "undefined" - undefined stars is the result in chrome however you should see You have seen/not seen "movie name" - "rating" stars.

我需要使用for循环来打印出我看过的每部电影并对其进行评级，以及是否看过电影。 问题是为什么它没有定义？ 代码是否应该看到movie.rating并在其中替换值？ 有人可以检查我的代码并为我的for循环提供帮助吗？

Answer 1

movies是一个数组movies movies.seen无法使用movies[i].seen和其他属性一样明智

Answer 2

将movies.seen ， movies.rating和movies.name更改为movies.seen movies[i].seen ， movies[i].seen movies[i].rating和movies[i].rating movies[i].name 。

Answer 3

使用索引访问数组的项目； 例如movies[i] ：

for (var i = 0; i < movies.length; i++) {
    var result = "You have ";
    if(movies[i].seen === true){
        result += "watched ";
    }
    else{
        result += "not seen ";
    }
    result += "\"" + movies[i].name + "\" - ";
    result += movies[i].rating + " stars"
    console.log(result)
}

或者，您可以将数组项存储在变量中，然后像这样使用它：

for (var i = 0; i < movies.length; i++) {
    var movie = movies[i];
    var result = "You have ";
    if (movie.seen) {
        result += "watched ";
    }
    else {
        result += "not seen ";
    }
    result += '"' + movie.name + '" - ';
    result += movie.rating + " stars";
    console.log(result);
}

Answer 4

这是一个工作正常的柱塞，供您查看它的正常工作。 :)

var movies = 
[
{name: "In Bruges", rating:"4.7", seen:false},
{name: "Frozen", rating: "4.5", seen:true},
{name: "Lion King", rating:"5", seen:true},
]


for (var i = 0; i < movies.length; i++) {
    var result = "You have ";
    if(movies[i].seen === true){
        result += "watched ";
    }
    else{
        result += "not seen ";
    }
    result += "\"" + movies[i].name + "\" - ";
    result += movies[i].rating + " stars"
    alert(result)
}

您试图访问的电影的属性seem ， name和rating ，但是电影有3个对象，索引从0到2。

Answer 5

您正在循环中使用影片，而影片不包含这些属性。 而且在迭代数组时使用forEach循环始终是安全的

做类似的事情

movies.forEach(function(movie){
var result = "You have ";
    if(movie.seen === true){
        result += "watched ";
    }
    else{
        result += "not seen ";
    }
    result +=  movie.name + " - ";
    result += movie.rating + " stars";
    console.log(result);

});

Answer 6

我建议使用其他方法迭代数组，并检查是否已看过电影。

 var movies = [ { name: "In Bruges", rating: "4.7", seen: false }, { name: "Frozen", rating: "4.5", seen: true }, { name: "Lion King", rating: "5", seen: true }, ]; movies.forEach(function (movie) { var result = "You have "; result += movie.seen ? "watched " : "not seen "; result += "\\"" + movie.name + "\\" - "; result += movie.rating + " stars" document.write(result + '<br>'); });