使用类创建角色的 JavaScript 功能
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【中文标题】使用类创建角色的 JavaScript 功能【英文标题】：JavaScript functionality to create roles with classes 【发布时间】：2021-12-20 03:04:21 【问题描述】：我的任务是实现在 JS 中创建角色的功能，每个角色都由其类型（访客、用户、管理员）定义。
-
Guest 类型应具有：获取任务数组的方法（constructor）；
获取任务 id（数组索引）并从任务数组中返回任务的方法（getTask）
不应定义 createTask 和 changeType
类型 User 也应该有 constructor 就像在 Guest 中一样，也是一个方法 getTask 和 createTask -a将新任务添加到任务数组的方法
不应定义 changeType。
Admin 类型应该有构造函数——一个获取客人和用户数组的方法；
getArray-返回客人和用户数组的方法
changeType - 一个获取数字（数组索引）的方法在提供的索引处修改数组项（将对象类型从访客更改为用户，否则，结果，任务应该从一种类型迁移到另一种类型），并返回修改后的项目数组
所以，我创建了所有的类和方法，但是在最后当我用 npm 测试它时，我得到的消息是：
来宾不应实现方法 createTask Guest 不应实现方法 changeType 用户不应实现方法 changeType 管理员应将角色类型从用户更改为访客但是当我在浏览器的控制台中引入它们时，一切正常，但我观察到当我编写 guest.createTask 时，它显示它未定义并且不会引发错误，但我认为我应该得到错误。
这是我的代码：
class Task
constructor(name)
this.name = name;
class Guest
constructor(tasks)
this.tasks = tasks;
getTask(index)
return this.tasks[index];
class User
constructor(tasks)
this.tasks = tasks;
getTask(index)
return this.tasks[index];
createTask(tasks)
return this.tasks.push(tasks);
class Admin
constructor(userGuestArray)
this.userGuestArray = userGuestArray;
getArray()
return this.userGuestArray;
changeType(index, replace, arr)
replace = this.userGuestArray;
arr = this.userGuestArray[index];
if (replace[index] = Guest)
replace[index] = new User(arr.tasks);
if (replace[index] = User)
replace[index] = new Guest(arr.tasks);
return replace;
这里是测试Guest类的代码：
const guest = new Guest(
[
new Task('task name 1'),
new Task('task name 2'),
new Task('task name 3'),
]
);
expect(guest.getTask(0).name).to.equal('task name 1');
expect(guest.getTask(2).name).to.equal('task name 3');
const guest = new Guest([]);
expect(guest.createTask).to.throw('method \'createTask\' is not defined');
expect(guest.changeType).to.throw('method \'changeType\' is not defined');
下面是管理员更改类型角色：
admin = new Admin([
new Guest([]),
new Guest([new Task('task name 1')]),
new User([]),
new User([new Task('task name 2')]),
]);
it('should change type of role from Guest to User', () =>
expect(admin.getArray()[0] instanceof Guest).to.equal(true);
admin.changeType(0);
expect(admin.getArray()[0] instanceof User).to.equal(true);
);
it('should change type of role from User to Guest', () =>
expect(admin.getArray()[3] instanceof User).to.equal(true);
admin.changeType(3);
expect(admin.getArray()[3] instanceof Guest).to.equal(true);
);
it('should move tasks from Guest to User, when change role', () =>
expect(admin.getArray()[1].getTask(0)).to.deep.equal( name: 'task name 1');
admin.changeType(1);
expect(admin.getArray()[1].getTask(0)).to.deep.equal( name: 'task name 1');
);
请帮助解决错误，我已经把我的大脑烧坏了。我试图将方法设为私有，但我认为我做的不对而且不起作用。我不知道该怎么办了。 PS：我是 JS 新手，正在尝试学习这些任务。
这是理解作业的整个测试脚本：
const Task, Guest, User, Admin = require('../src');
const chai = require('chai');
const expect = chai;
describe('Guest', () =>
it('should have method getTask', () =>
const guest = new Guest(
[
new Task('task name 1'),
new Task('task name 2'),
new Task('task name 3'),
]
);
console.log(1,guest);
expect(guest.getTask(0).name).to.equal('task name 1');
console.log(2,guest.getTask(0).name);
expect(guest.getTask(2).name).to.equal('task name 3');
console.log(3,guest.getTask(2).name);
);
it('should not implement method createTask', () =>
const guest = new Guest([]);
console.log(4,guest);
expect(guest.createTask).to.throw('method \'createTask\' is not defined');
console.log(5,guest.createTask);
);
it('should not implement method changeType', () =>
const guest = new Guest([]);
console.log(6,guest);
expect(guest.changeType).to.throw('method \'changeType\' is not defined');
console.log(7,guest.changeType);
);
);
describe('User', () =>
let user;
beforeEach(() =>
user = new User(
[
new Task('task name 1'),
new Task('task name 2'),
new Task('task name 3'),
]
);
)
console.log(8,user);
it('should have method getTask', () =>
expect(9,user.getTask(0).name).to.equal('task name 1');
console.log(user.getTask(0).name)
expect(10,user.getTask(2).name).to.equal('task name 3');
);
it('should have method createTask', () =>
expect(user.getTask(0).name).to.equal('task name 1');
console.log(11,user.getTask(0).name);
expect(user.getTask(2).name).to.equal('task name 3');
console.log(12,user.getTask(2).name);
user.createTask(new Task('task name 4'))
console.log(13,user.createTask(new Task('task name 4')));
expect(user.getTask(3).name).to.equal('task name 4');
console.log(14,user.getTask(3).name);
);
it('should not implement method changeType', () =>
const user = new Guest([]);
console.log(15,user);
expect(user.changeType).to.throw('method \'changeType\' is not defined');
console.log(16,user.changeType);
);
);
describe('Admin', () =>
let admin;
beforeEach(() =>
admin = new Admin([
new Guest([]),
new Guest([new Task('task name 1')]),
new User([]),
new User([new Task('task name 2')]),
]);
)
console.log(17,admin);
it('should have method getArray', () =>
expect(admin.getArray().length).to.equal(4);
);
console.log(18,admin.getArray().length);
it('should return instance of Guest as a first element by the method getArray', () =>
expect(admin.getArray()[0]).to.deep.equal( tasks: []);
);
console.log(19,admin.getArray()[0]);
it('should return instance of User as a third element by the method getArray', () =>
expect(admin.getArray()[3]).to.deep.equal( tasks: [ name: 'task name 2']);
);
console.log(20,(admin.getArray()[3]));
it('should return array of roles by the method getArray', () =>
expect(admin.getArray()).to.deep.equal([ tasks: [], tasks: [ name: 'task name 1'], tasks: [], tasks: [ name: 'task name 2']]);
);
console.log(21,admin.getArray())
it('should change type of role from Guest to User', () =>
expect(admin.getArray()[0] instanceof Guest).to.equal(true);
console.log(22,admin.getArray()[0] instanceof Guest);
admin.changeType(0);
console.log(23, admin.changeType(0));
expect(admin.getArray()[0] instanceof User).to.equal(true);
console.log(24,admin.getArray()[0] instanceof User);
);
it('should change type of role from User to Guest', () =>
expect(admin.getArray()[3] instanceof User).to.equal(true);
console.log(25,admin.getArray()[3] instanceof User);
admin.changeType(3);
console.log(26,admin.changeType(3));
expect(admin.getArray()[3] instanceof Guest).to.equal(true);
console.log(27,admin.getArray()[3] instanceof Guest)
);
it('should move tasks from Guest to User, when change role', () =>
expect(admin.getArray()[1].getTask(0)).to.deep.equal( name: 'task name 1');
console.log(28,admin.getArray()[1].getTask(0));
admin.changeType(1);
console.log(29,admin.changeType(1));
expect(admin.getArray()[1].getTask(0)).to.deep.equal( name: 'task name 1');
console.log(30,admin.getArray()[1].getTask(0));
);
);
不要关注控制台日志，我尝试调试我的代码以查看错误在哪里。 错误日志：
<?xml version="1.0" encoding="UTF-8"?>
<testsuites name="Mocha Tests" time="0.0090" tests="13" failures="5">
<testsuite name="Root Suite" timestamp="2021-11-06T12:36:46" tests="0" time="0.0000" failures="0">
</testsuite>
<testsuite name="Guest" timestamp="2021-11-06T12:36:46" tests="3" file="C:\Users\artio\Desktop\6 Classes\8.2.classes\test\index.js" time="0.0040" failures="2">
<testcase name="Guest should have method getTask" time="0.0010" classname="should have method getTask">
</testcase>
<testcase name="Guest should not implement method createTask" time="0.0010" classname="should not implement method createTask">
<failure message="expected undefined to be a function" type="AssertionError"><![CDATA[AssertionError: expected undefined to be a function
at Context.<anonymous> (test\index.js:21:38)
at processImmediate (internal/timers.js:439:21)]]></failure>
</testcase>
<testcase name="Guest should not implement method changeType" time="0.0000" classname="should not implement method changeType">
<failure message="expected undefined to be a function" type="AssertionError"><![CDATA[AssertionError: expected undefined to be a function
at Context.<anonymous> (test\index.js:26:38)
at processImmediate (internal/timers.js:439:21)]]></failure>
</testcase>
</testsuite>
<testsuite name="User" timestamp="2021-11-06T12:36:46" tests="3" file="C:\Users\artio\Desktop\6 Classes\8.2.classes\test\index.js" time="0.0010" failures="2">
<testcase name="User should have method getTask" time="0.0000" classname="should have method getTask">
<failure message="task name 1: expected 9 to equal 'task name 1'" type="AssertionError"><![CDATA[AssertionError: task name 1: expected 9 to equal 'task name 1'
at Context.<anonymous> (test\index.js:42:43)
at processImmediate (internal/timers.js:439:21)]]></failure>
</testcase>
<testcase name="User should have method createTask" time="0.0000" classname="should have method createTask">
</testcase>
<testcase name="User should not implement method changeType" time="0.0000" classname="should not implement method changeType">
<failure message="expected undefined to be a function" type="AssertionError"><![CDATA[AssertionError: expected undefined to be a function
at Context.<anonymous> (test\index.js:55:41)
at processImmediate (internal/timers.js:439:21)]]></failure>
</testcase>
</testsuite>
<testsuite name="Admin" timestamp="2021-11-06T12:36:46" tests="7" file="C:\Users\artio\Desktop\6 Classes\8.2.classes\test\index.js" time="0.0020" failures="1">
<testcase name="Admin should have method getArray" time="0.0000" classname="should have method getArray">
</testcase>
<testcase name="Admin should return instance of Guest as a first element by the method getArray" time="0.0000" classname="should return instance of Guest as a first element by the method getArray">
</testcase>
<testcase name="Admin should return instance of User as a third element by the method getArray" time="0.0000" classname="should return instance of User as a third element by the method getArray">
</testcase>
<testcase name="Admin should return array of roles by the method getArray" time="0.0010" classname="should return array of roles by the method getArray">
</testcase>
<testcase name="Admin should change type of role from Guest to User" time="0.0000" classname="should change type of role from Guest to User">
<failure message="expected false to equal true" type="AssertionError"><![CDATA[AssertionError: expected false to equal true
at Context.<anonymous> (test\index.js:84:56)
at processImmediate (internal/timers.js:439:21)]]></failure>
</testcase>
<testcase name="Admin should change type of role from User to Guest" time="0.0000" classname="should change type of role from User to Guest">
</testcase>
<testcase name="Admin should move tasks from Guest to User, when change role" time="0.0000" classname="should move tasks from Guest to User, when change role">
</testcase>
</testsuite>
</testsuites>
【问题讨论】：
你为什么期望guest.createTask 抛出？当您访问不存在的对象的属性时，JS 的行为一直是返回undefined。如果您尝试实际调用该方法，您会得到一个异常，但您没有这样做
是的，我明白了，但我认为我应该得到一个参考错误，即 createTask 未定义或如何调用该错误。 "expect(guest.createTask).to.throw('方法\'createTask\'未定义');"
不，你不应该——这不是 JS 的工作方式。它返回undefined，这是语言标准定义它的方式
再次，您希望抛出的错误消息不存在。因此，断言将失败。而且我真的不知道为什么你想要一个依赖特定错误消息的脆弱代码，而不是直接测试给定属性不是方法（或测试它不存在）。
如果你想专门依赖那些错误信息，那么你可以在Guest中添加createTask方法，让它抛出一个与错误信息匹配的错误断言。如果您不想真正修复它以使其正确，这是使此代码正常工作的唯一方法。
【参考方案1】：
这是我如何完成这项任务的，一点也不难，但令人困惑：
class Task
constructor(name)
this.name = name;
class Guest
constructor(tasks)
this.tasks = tasks;
getTask(index)
return this.tasks[index];
createTask()
throw new Error("method 'createTask' is not defined");
changeType()
throw new Error("method 'changeType' is not defined");
class User
constructor(tasks)
this.tasks = tasks;
getTask(index)
return this.tasks[index];
createTask(tasks)
return this.tasks.push(tasks);
changeType()
throw new Error("method 'changeType' is not defined");
class Admin
constructor(userGuestArray)
this.userGuestArray = userGuestArray;
getArray()
return this.userGuestArray;
changeType(index)
let mainArray = this.userGuestArray;
let arr = this.userGuestArray[index];
if (mainArray[index] instanceof Guest)
mainArray[index] = new User(arr.tasks);
else if (mainArray[index] instanceof User)
mainArray[index] = new Guest(arr.tasks);
return mainArray;
module.exports.Task = Task;
module.exports.Guest = Guest;
module.exports.User = User;
module.exports.Admin = Admin;
对于错误部分，我应该只抛出一个，这就是为什么我在测试时遇到错误，消息是我应该抛出一个错误
【讨论】：
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