javascript - 如何删除属性(property)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

如何删除属性编号，因为删除 Student.number 不起作用。

Answer 1

...as the delete Student.number is not working

Student 没有 number 属性，所以没有什么可以删除的。使用 new Student 创建的对象可以。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

如果你想创建一个 Student 版本来创建没有 number 属性的对象，那是可能的，但这是个坏主意:

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 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

这是个坏主意，因为以这种方式设置继承，子类实例 (NumberlessStudent) 应该具有父类(super class) (Student) 实例的特性。