Question

我有这个功能

    function getStudents() {
                    var students = [];
                    students[0] = {name: "Anna", mark: 65, sex: "female"};
                    students[1] = {name: "James", mark:33, sex: "male"};
                    students[2] = {name: "William", mark: 87, sex: "male"};
                    students[3] = {name: "Jane", mark: 72, sex: "female"};
                    students[4] = {name: "Rikki", mark: 60, sex: "male"};
                    students[5] = {name: "Angela", mark: 58, sex: "female"};    
            }

然后在身体中我尝试这样做：

        var students = getStudents();

        var referrals = ["James", "Angela"];
                for(var i = 0; i < students.length; i++){
        var pTag ="<p>";

然而，一旦我尝试通过循环，它告诉我它不能做.min的未定义变量，但我想我已经通过调用函数并将其分配给变量来定义它？

Answer 1

更改此代码的功能。问题是你没有返回变量学生，当你超出范围时，变量不再存在。返回时，您将在调用函数时将其分配给变量。

function getStudents() {
                var students = [];
                students[0] = {name: "Anna", mark: 65, sex: "female"};
                students[1] = {name: "James", mark:33, sex: "male"};
                students[2] = {name: "William", mark: 87, sex: "male"};
                students[3] = {name: "Jane", mark: 72, sex: "female"};
                students[4] = {name: "Rikki", mark: 60, sex: "male"};
                students[5] = {name: "Angela", mark: 58, sex: "female"};    
                return students;            
}

Answer 2

你应该echo $don;变量

void f() {
    d();
}

void d() {
}

Answer 3

您需要在函数末尾返回students数组，以便从getStudents为变量分配数组：

function getStudents() {
     var students = [];
     students[0] = {name: "Anna", mark: 65, sex: "female"};
     students[1] = {name: "James", mark:33, sex: "male"};
     students[2] = {name: "William", mark: 87, sex: "male"};
     students[3] = {name: "Jane", mark: 72, sex: "female"};
     students[4] = {name: "Rikki", mark: 60, sex: "male"};
     students[5] = {name: "Angela", mark: 58, sex: "female"}; 
     return students;   
}

否则你说var students = getStudents();它只是在做函数调用而不是分配数组。

Answer 4

您无法在创建对象的函数调用中请求未返回的对象的长度。您没有为学生变量分配任何内容，因为getStudents（）函数不会返回值或对象，从而导致您获得错误。

在下面的jsfiddle上使用开发者控制台来查看演示

jsFiddle

function getStudents() {
    var students = [];
  students[0] = {name: "Anna", mark: 65, sex: "female"};
  students[1] = {name: "James", mark:33, sex: "male"};
  students[2] = {name: "William", mark: 87, sex: "male"};
  students[3] = {name: "Jane", mark: 72, sex: "female"};
  students[4] = {name: "Rikki", mark: 60, sex: "male"};
  students[5] = {name: "Angela", mark: 58, sex: "female"};  

  return students;
}

var students = getStudents();
//var referrals = ["James", "Angela"];
console.log(students);

为什么我的变量未定义

4 个答案: