Question

我的代码：

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Test</title>
</head>

<body>
    <script>
        var students = [];
        var student = {};
        var scores = [];
        var final = [];

        function setStudent(name , score) {
            student = {"Name": name, "Score": score};
            //student.Name = name;
            //student.Score = score;
            document.write(student.Name + " scored " + student.Score + ".<br>");
            final.push(student);
            return student;

        }


        for (var i=0; i<4; i++) {
            students.push(prompt("Please Enter student name"));
        }

        for (var i=0; i<4; i++) {
            scores.push(prompt("Please Enter "+ students[i] +"'s score" ))
        }
        for (var i=0; i<4; i++) {
            setStudent(students[i],scores[i]);

        }

        console.log(final);
    </script>
</body>
</html>

这是第一个有效的版本，控制台输出如下所示： Image can be found at http://i.imgur.com/HnEHX5J.png

虽然第二个版本是：

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Test</title>
</head>

<body>
    <script>
        var students = [];
        var student = {};
        var scores = [];
        var final = [];

        function setStudent(name , score) {
            //student = {"Name": name, "Score": score};
            student.Name = name;
            student.Score = score;
            document.write(student.Name + " scored " + student.Score + ".<br>");
            final.push(student);
            return student;

        }


        for (var i=0; i<4; i++) {
            students.push(prompt("Please Enter student name"));
        }

        for (var i=0; i<4; i++) {
            scores.push(prompt("Please Enter "+ students[i] +"'s score" ))
        }
        for (var i=0; i<4; i++) {
            setStudent(students[i],scores[i]);

        }

        console.log(final);
    </script>
</body>
</html>

此版本的输出是： You can find image at https://i.stack.imgur.com/0mQFz.png

万一你不知道改变了什么，看看分配对象的功能我的问题是为什么输出不同。

Answer 1

您未在student函数中声明变量setStudent。因此，the variable student is defined on the global object window。运行此方法时，每次都使用相同的指针，从而更改同一指针的值并将相同的对象重新添加到数组中。

要解决此错误，只需将student声明为空对象文字{}

我的问题是为什么输出不同

输出不同的原因是document.write会将当前点的对象及时转换为string。在console.log中，在console.log中展开箭头时，抓取对象的子属性。如果您在每次分配后克隆了对象或使用了JSON.stringify，然后console.log使用了console.log，那么var students = []; var student = {}; var scores = []; var final = []; function setStudent(name, score) { //student = {"Name": name, "Score": score}; // ERROR HERE // you're not declaring the variable `student` therefore, the variable `student` is defined on the global object `window`. When you run this method, you're using the same pointer every time and thus changing the pointer and readding it to the array. var student = {}; // this is the fix student.Name = name; student.Score = score; document.write(student.Name + " scored " + student.Score + ".<br>"); final.push(student); return student; } for (var i = 0; i < 4; i++) { students.push(prompt("Please Enter student name")); } for (var i = 0; i < 4; i++) { scores.push(prompt("Please Enter " + students[i] + "'s score")) } for (var i = 0; i < 4; i++) { setStudent(students[i], scores[i]); } console.log(final);的输出将符合预期。

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使用console.log，对象数组中的Javascript对象是不同的

1 个答案: