如何删除财产编号？

Question

function Student(name, sclass, year, number, submissionYear)
{
     this.name = name;
     this.sclass = sclass;
     this.year = year;
     this.number = number;
     this.submissionYear = submissionYear;
}

// Edit : added OP's code from comments
let Manuel = new Student("Manuel", "lesi", "3", "98789", 2014);
console.log(Manuel.number);
delete Student.number;
console.log(Student); // The object still includes number as property

我如何删除属性号，因为删除Student.number无效。

Answer 1

...因为删除Student.number不起作用

Student没有number属性，因此没有要删除的内容。用new Studentdo 创建的对象。因此，例如：

function Student(name, sclass, year, number, submissionYear)
{
    this.name = name;
    this.sclass = sclass;
    this.year = year;
    this.number = number;
    this.submissionYear = submissionYear;
}

var s = new Student();
console.log("number" in s); // true
delete s.number;
console.log("number" in s); // false

如果要创建一个版本，Student该版本创建没有number属性的对象，那是可能的，但这是一个坏主意：

function Student(name, sclass, year, number, submissionYear)
{
    this.name = name;
    this.sclass = sclass;
    this.year = year;
    this.number = number;
    this.submissionYear = submissionYear;
}

function NumberlessStudent() {
    Student.apply(this, arguments);
    delete this.number;
}
NumberlessStudent.prototype = Object.create(Student.prototype);
NumberlessStudent.prototype.constructor = NumberlessStudent;

var n = new NumberlessStudent();
console.log("number" in n); // false

或者最好在ES2015 +中使用以下class语法：

class Student {
    constructor(name, sclass, year, number, submissionYear) {
        this.name = name;
        this.sclass = sclass;
        this.year = year;
        this.number = number;
        this.submissionYear = submissionYear;
    }
}

class NumberlessStudent extends Student {
    constructor(...args) {
        super(...args);
        delete this.number;
    }
}

const n = new NumberlessStudent();
console.log("number" in n); // false

这是一个坏主意，因为以这种方式设置继承时，子类实例（NumberlessStudent）应该具有超类（Student）实例的功能。

Answer 2

您Student是一个构造函数，因此Student.number除非它是静态方法，否则是不正确的（但这不是您的情况）。

您必须创建一个对象Student，即

const student = new Student('Mell', 'A', 1990, 500, 1994);

那你可以用

delete student.number

请以以下代码段为例：

const student = new Student('Mell', 'A', 1990, 500, 1994);

您可以在此处找到有关JavaScript中的构造函数和对象的更多信息。