Question

我希望在gradebook对象中添加addScore以追加传入分数数组的分数。但它给了我一个错误。

TypeError：无法读取未定义的属性'testScore'

var students = ["Joseph", "Susan", "William", "Elizabeth"];

var scores = [ [80, 70, 70, 100],
               [85, 80, 90, 90],
               [75, 70, 80, 75],
               [100, 90, 95, 85] ];


var gradebook = {
  joseph:{testScore:scores[0]},
  susan:{testScore:scores[1]},
  william:{testScore:scores[2]},
  elizabeth:{testScore:scores[3]},
  addGrade:function(stu_name,grade) {
    gradebook.stu_name.testScore.push(grade);
  }
};

//test call
gradebook.addGrade("susan",100);
console.log(gradebook.susan.testScore); //should display [85 80 90 90 100]

Answer 1

您不能对动态属性名称使用“点”表示法。但您可以使用括号表示法：

gradebook["joseph"]
// is equivalent to
gradebook.joseph

...但括号中的表达式可以是一个变量，其值为具有您的属性名称的字符串：

var p = "joseph";
gradebook[p]

因此，对于addGrade()函数，请尝试以下操作：

addGrade:function(stu_name,grade) {
  gradebook[stu_name].testScore.push(grade);
}

Answer 2

使用此：

var gradebook = {
  joseph:{testScore:scores[0]},
  susan:{testScore:scores[1]},
  william:{testScore:scores[2]},
  elizabeth:{testScore:scores[3]},
  addGrade:function(stu_name,grade) {
    gradebook[stu_name].testScore.push(grade);
  }
};

Answer 3

Here is working demo

数组索引使用方括号，请尝试：

gradebook[stu_name].testScore.push(grade);

关于给出TypeError的对象函数的初学者javascript

3 个答案: