使用ES6模块导出/导入单类方法? [英] export / import single class method using ES6 modules?

问题描述

假设我在fileA.js中有一个像这样的简单类:

Let's say I have a simple class like this in fileA.js:

class foo {
    constructor(x) {
        this.name = x
    }

    fooMethod(x) {
        return x + 'hello';
    }
}

我想像这样在fileB.js中导入和使用fooMethod:

And I want to import and use fooMethod in fileB.js like this:

import { fooMethod } from './fileA';

class bar() {
    ...
    barMethod(x) {
        return fooMethod(x);
    }
}

我该如何在fileA中编写export来实现这一目标?

How would I write the export in fileA to achieve this?

推荐答案

您必须将其导出到原型中.但是请记住，如果这样做，您将不会在类/对象上下文中调用该函数:

You would have to export it on the prototype. But remember that if you do that you won't call the function in the class/object context:

export foo.prototype. fooMethod

但是我建议您不要这样做.

However I would recommend you to not to do so.

好的，由于您的评论，您希望有一个很好的方法来为两个类提供通用功能，而这些功能不会扩展同一基类.一种简单的方法是从两个类中导入实用程序函数:

Okay, due to your comment you want a good way to have a common functionality for two classes, that don't extend the same base class. One simple way is to import a utility function from two classes:

foo.js

export function foo() {
  return this.name;
}

a.js

import {foo} from 'foo';
export class A extends BaseA {
  foo() {
    foo.apply(this, arguments);
  }
}

b.js

import {foo} from 'foo';
export class B extends BaseB {
  foo() {
    foo.apply(this, arguments);
  }
}

这是一个很好的模式，并且对于单个功能很好地工作，但是如果您想应用更复杂的功能，则存在局限性.实现此目的的一种好方法是混合模式:

This is a good pattern and works well for a single function, but has limits if you want to apply more complex functionality. A good way to achieve this is a mixing pattern:

foo.js

export default superClass => class extends superClass {
  foo() {
    return this.name;
  }
};

a.js

import foo from 'foo';
export class A extends foo(BaseA) {
  ..
}

b.js

import foo from 'foo';
export class B extends foo(BaseB) {
  ..
}

这将使您的混合在类'A'/'B'和'BaseA'/'BaseB'之间创建一个新的匿名类，该类提供了通用功能foo.

This will make your mixing create a new anonymous class between your class 'A'/'B' and 'BaseA'/'BaseB', which provides the common function foo.

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