Javascript ES 6-使用类

我正在学习ES6类的语法。我有C#的背景，如果我的术语不正确，我道歉。或者，如果我正在做一些看起来很奇怪的事情

我正在构建一个web应用程序作为学习练习。它构建在Node和Express上。我有一些路线定义如下：

'use strict';

module.exports = function() {
    const app = this;

    app.use('/blog', function(req, res) {
        console.log('loading blog postings');        
        res.render('blog', {}); 
    });

    app.use('/', function(req, res) {
        console.log('looking up: ' + req.path);
        res.render('home', {});
    });
};

'use strict';

module.exports = function() {
    const app = this;
    const ViewModels = require('../viewModels/index');

    app.use('/blog', function(req, res) {
        console.log('loading blog postings');
        let viewModel = new ViewModels.BlogViewModel();
        res.render('blog', viewModel); 
    });

    app.use('/', function(req, res) {
        console.log('looking up: ' + req.path);
        let viewModel = new ViewModels.HomeViewModel();
        res.render('home', viewModel);
    });
};

我试图在这些视图后面放置一些视图模型。因此，我有一个名为

viewModels

的目录。该目录包含以下文件：

index.js
blog.js
home.js

当前的文件可能不准确，如下所示：

'use strict';

module.exports = function() {
    const app = this;

    app.use('/blog', function(req, res) {
        console.log('loading blog postings');        
        res.render('blog', {}); 
    });

    app.use('/', function(req, res) {
        console.log('looking up: ' + req.path);
        res.render('home', {});
    });
};

'use strict';

module.exports = function() {
    const app = this;
    const ViewModels = require('../viewModels/index');

    app.use('/blog', function(req, res) {
        console.log('loading blog postings');
        let viewModel = new ViewModels.BlogViewModel();
        res.render('blog', viewModel); 
    });

    app.use('/', function(req, res) {
        console.log('looking up: ' + req.path);
        let viewModel = new ViewModels.HomeViewModel();
        res.render('home', viewModel);
    });
};

index.js

'use strict';

module.exports = function() {
  const HomeViewModel = require('./home);
  const BlogViewModel = require('./blog);
};

export default class BlogViewModel {
    constructor() {
        this.title = 'My Blog';
    }
}

export default class HomeViewModel {
    constructor() {
        this.title = 'Home';
    }
}

'use strict';
//This module can be used within the class. However, you cannot use it in another file.
const AModule = require('AModule');
//The class name used here just for debug output.
module.exports = class AClass {
  constructor(startValue) {
    //Not like C#. JavaScript does not define private or public.
    this.value = startValue;
  }
  method(incValue) {
    this.value += incValue;
    AModule(); //Just show you can use this module within the class;
  }
}

'use strict';
//You need to put a ./ before the path if you are include another module made by yourself.
//You do not need it for a npm module.
const AClass = require('./AClass.js');
//Now you just required the class of the AClass, you still need to new one;
var aClass = new AClass(500);
//After new one, you can call its method.
aClass.method(30);
//You can access its property by a dot;
console.info(aClass.value); //530

blog.js

'use strict';

module.exports = function() {
  const HomeViewModel = require('./home);
  const BlogViewModel = require('./blog);
};

export default class BlogViewModel {
    constructor() {
        this.title = 'My Blog';
    }
}

export default class HomeViewModel {
    constructor() {
        this.title = 'Home';
    }
}

'use strict';
//This module can be used within the class. However, you cannot use it in another file.
const AModule = require('AModule');
//The class name used here just for debug output.
module.exports = class AClass {
  constructor(startValue) {
    //Not like C#. JavaScript does not define private or public.
    this.value = startValue;
  }
  method(incValue) {
    this.value += incValue;
    AModule(); //Just show you can use this module within the class;
  }
}

'use strict';
//You need to put a ./ before the path if you are include another module made by yourself.
//You do not need it for a npm module.
const AClass = require('./AClass.js');
//Now you just required the class of the AClass, you still need to new one;
var aClass = new AClass(500);
//After new one, you can call its method.
aClass.method(30);
//You can access its property by a dot;
console.info(aClass.value); //530

home.js

'use strict';

module.exports = function() {
  const HomeViewModel = require('./home);
  const BlogViewModel = require('./blog);
};

export default class BlogViewModel {
    constructor() {
        this.title = 'My Blog';
    }
}

export default class HomeViewModel {
    constructor() {
        this.title = 'Home';
    }
}

'use strict';
//This module can be used within the class. However, you cannot use it in another file.
const AModule = require('AModule');
//The class name used here just for debug output.
module.exports = class AClass {
  constructor(startValue) {
    //Not like C#. JavaScript does not define private or public.
    this.value = startValue;
  }
  method(incValue) {
    this.value += incValue;
    AModule(); //Just show you can use this module within the class;
  }
}

'use strict';
//You need to put a ./ before the path if you are include another module made by yourself.
//You do not need it for a npm module.
const AClass = require('./AClass.js');
//Now you just required the class of the AClass, you still need to new one;
var aClass = new AClass(500);
//After new one, you can call its method.
aClass.method(30);
//You can access its property by a dot;
console.info(aClass.value); //530

我的想法是，我可以使用

index.js

来定义我的包或名称空间。然后，在我的路由代码中，我可以这样做：

'use strict';

module.exports = function() {
    const app = this;

    app.use('/blog', function(req, res) {
        console.log('loading blog postings');        
        res.render('blog', {}); 
    });

    app.use('/', function(req, res) {
        console.log('looking up: ' + req.path);
        res.render('home', {});
    });
};

'use strict';

module.exports = function() {
    const app = this;
    const ViewModels = require('../viewModels/index');

    app.use('/blog', function(req, res) {
        console.log('loading blog postings');
        let viewModel = new ViewModels.BlogViewModel();
        res.render('blog', viewModel); 
    });

    app.use('/', function(req, res) {
        console.log('looking up: ' + req.path);
        let viewModel = new ViewModels.HomeViewModel();
        res.render('home', viewModel);
    });
};

---

但是，当我尝试此操作时，会出现一些运行时错误，如“错误：找不到模块“../viewModels/index”。这意味着我没有正确设置模块。但是，看起来好像是我做错了什么？

您的

index.js

文件不正确，您不能从那里导出ViewModels。将其更改为：

'use strict';

module.exports = {
  HomeViewModel: require('./home'),
  BlogViewModel: require('./blog')
};

而且。。。viewModels它对C#有好处，但对Node.js没有好处。在节点中，它应该只是模型，IMO

更新：

---

Node.js不完全支持所有ES6功能，尤其是新模块声明：。应使用标准CommonJs模块声明导出函数：

'use strict';

class HomeViewModel {
  constructor() {
    this.title = 'Home';
  }
}

module.exports = HomeViewModel;

---

事实上，我不确定你想问什么。如果我回答错了，没关系

首先，您得到错误的原因是：找不到模块“../viewModels/index”，因为您在那里放了两个点。应该只有一个点意味着从这里开始。然而，我不确定这是否是问题所在。我想问你把路由代码放在哪里，但我还没有评论的权限。（啊…你在开玩笑吧…）

其次，这里是在ES6中导出类的正确方法

例如：

AClass.js

'use strict';

module.exports = function() {
  const HomeViewModel = require('./home);
  const BlogViewModel = require('./blog);
};

export default class BlogViewModel {
    constructor() {
        this.title = 'My Blog';
    }
}

export default class HomeViewModel {
    constructor() {
        this.title = 'Home';
    }
}

'use strict';
//This module can be used within the class. However, you cannot use it in another file.
const AModule = require('AModule');
//The class name used here just for debug output.
module.exports = class AClass {
  constructor(startValue) {
    //Not like C#. JavaScript does not define private or public.
    this.value = startValue;
  }
  method(incValue) {
    this.value += incValue;
    AModule(); //Just show you can use this module within the class;
  }
}

'use strict';
//You need to put a ./ before the path if you are include another module made by yourself.
//You do not need it for a npm module.
const AClass = require('./AClass.js');
//Now you just required the class of the AClass, you still need to new one;
var aClass = new AClass(500);
//After new one, you can call its method.
aClass.method(30);
//You can access its property by a dot;
console.info(aClass.value); //530

main.js

'use strict';

module.exports = function() {
  const HomeViewModel = require('./home);
  const BlogViewModel = require('./blog);
};

export default class BlogViewModel {
    constructor() {
        this.title = 'My Blog';
    }
}

export default class HomeViewModel {
    constructor() {
        this.title = 'Home';
    }
}

'use strict';
//This module can be used within the class. However, you cannot use it in another file.
const AModule = require('AModule');
//The class name used here just for debug output.
module.exports = class AClass {
  constructor(startValue) {
    //Not like C#. JavaScript does not define private or public.
    this.value = startValue;
  }
  method(incValue) {
    this.value += incValue;
    AModule(); //Just show you can use this module within the class;
  }
}

'use strict';
//You need to put a ./ before the path if you are include another module made by yourself.
//You do not need it for a npm module.
const AClass = require('./AClass.js');
//Now you just required the class of the AClass, you still need to new one;
var aClass = new AClass(500);
//After new one, you can call its method.
aClass.method(30);
//You can access its property by a dot;
console.info(aClass.value); //530

这是在ES6中创建类的100%工作方式

以下是详细的文档：

无论如何，Javascript中的类就像函数一样，函数的

原型将是它的方法
new Class（）
只是创建一个对象，使用object作为
this
运行函数类（与
Class.bind（obj，parameters）
相同），然后将新对象的构造函数属性链接到所使用的函数

module.exports=xxx只是将xxx作为该模块的值。例如，如果您
module.exports='Hello'和
控制台信息（需要（'module'），您将得到Hello
 没关系，问题是他没有调用函数，但这也是一个解决方案，即使他会调用函数，他的代码也不会工作。他在一个函数中定义常量，这些常量在函数外部是不可见的。@AlexanderMac当我使用这种方法时，
let viewModel=new ViewModels.HomeViewModel（）行抛出
错误：路由：/-ViewModels.HomeViewModel不是一个函数
Node.js不完全支持所有ES6功能，尤其是新模块声明：。使用标准CommonJs模块声明导出函数：
module.exports=HomeViewModel
@AlexanderMac执行
module.exports=HomeViewModel您提到的方法是否替换您答案中的行？或者，是在你答案的最后一个分号之后吗？你不应该将commonjs与ES6模块混合使用。@Bergi-那么，推荐的方法是什么？我正在努力学习这些东西，有很多例子。很难知道什么是好方法，什么是差方法，以及仅仅因为另一个依赖的框架正在使用的方法而做了什么。我建议您使用
index.js
。