有没有办法在 ES6 / Node 4 中创建接口？

Question

ES6 在 Node 4 中完全可用。我想知道它是否包含定义方法契约的接口概念，如 MyClass implements MyInterface 。

我用谷歌搜索找不到太多东西，但也许有一个不错的技巧或解决方法可用。

原文由 Jérôme Verstrynge 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

接口不是 ES6 的一部分，但类是。

如果你真的需要它们，你应该看看 支持它们 的 TypeScript 。

原文由 gaelgillard 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

这是我解决问题的方法。您可以通过用另一个接口覆盖一个接口来“实现”多个接口。

 class MyInterface {
  // Declare your JS doc in the Interface to make it acceable while writing the Class and for later inheritance
  /**
   * Gives the sum of the given Numbers
   * @param {Number} a The first Number
   * @param {Number} b The second Number
   * @return {Number} The sum of the Numbers
   */
  sum(a, b) {
    this._WARNING('sum(a, b)');
  }

  // delcare a warning generator to notice if a method of the interface is not overridden
  // Needs the function name of the Interface method or any String that gives you a hint ;)
  _WARNING(fName = 'unknown method') {
    console.warn('WARNING! Function "' + fName + '" is not overridden in ' + this.constructor.name);
  }
}

class MultipleInterfaces extends MyInterface {
  // this is used for "implement" multiple Interfaces at once
  /**
   * Gives the square of the given Number
   * @param {Number} a The Number
   * @return {Number} The square of the Numbers
   */
  square(a) {
    this._WARNING('square(a)');
  }
}

class MyCorrectUsedClass extends MyInterface {
  // You can easy use the JS doc declared in the interface
  /** @inheritdoc */
  sum(a, b) {
    return a + b;
  }
}
class MyIncorrectUsedClass extends MyInterface {
  // not overriding the method sum(a, b)
}

class MyMultipleInterfacesClass extends MultipleInterfaces {
  // nothing overriden to show, that it still works
}

let working = new MyCorrectUsedClass();

let notWorking = new MyIncorrectUsedClass();

let multipleInterfacesInstance = new MyMultipleInterfacesClass();

// TEST IT

console.log('working.sum(1, 2) =', working.sum(1, 2));
// output: 'working.sum(1, 2) = 3'

console.log('notWorking.sum(1, 2) =', notWorking.sum(1, 2));
// output: 'notWorking.sum(1, 2) = undefined'
// but also sends a warn to the console with 'WARNING! Function "sum(a, b)" is not overridden in MyIncorrectUsedClass'

console.log('multipleInterfacesInstance.sum(1, 2) =', multipleInterfacesInstance.sum(1, 2));
// output: 'multipleInterfacesInstance.sum(1, 2) = undefined'
// console warn: 'WARNING! Function "sum(a, b)" is not overridden in MyMultipleInterfacesClass'

console.log('multipleInterfacesInstance.square(2) =', multipleInterfacesInstance.square(2));
// output: 'multipleInterfacesInstance.square(2) = undefined'
// console warn: 'WARNING! Function "square(a)" is not overridden in MyMultipleInterfacesClass'

编辑：

我改进了代码，因此您现在可以在 --- 中简单地使用 implement(baseClass, interface1, interface2, ...) extends 。

 /**
 * Implements any number of interfaces to a given class.
 * @param cls The class you want to use
 * @param interfaces Any amount of interfaces separated by comma
 * @return The class cls exteded with all methods of all implemented interfaces
 */
function implement(cls, ...interfaces) {
  let clsPrototype = Object.getPrototypeOf(cls).prototype;
  for (let i = 0; i < interfaces.length; i++) {
    let proto = interfaces[i].prototype;
    for (let methodName of Object.getOwnPropertyNames(proto)) {
      if (methodName !== 'constructor')
        if (typeof proto[methodName] === 'function')
          if (!clsPrototype[methodName]) {
            console.warn('WARNING! "' + methodName + '" of Interface "' + interfaces[i].name + '" is not declared in class "' + cls.name + '"');
            clsPrototype[methodName] = proto[methodName];
          }
    }
  }
  return cls;
}

// Basic Interface to warn, whenever an not overridden method is used
class MyBaseInterface {
  // declare a warning generator to notice if a method of the interface is not overridden
  // Needs the function name of the Interface method or any String that gives you a hint ;)
  _WARNING(fName = 'unknown method') {
    console.warn('WARNING! Function "' + fName + '" is not overridden in ' + this.constructor.name);
  }
}

// create a custom class
/* This is the simplest example but you could also use
 *
 *  class MyCustomClass1 extends implement(MyBaseInterface) {
 *      foo() {return 66;}
 *  }
 *
 */
class MyCustomClass1 extends MyBaseInterface {
  foo() {
    return 66;
  }
}

// create a custom interface
class MyCustomInterface1 {
  // Declare your JS doc in the Interface to make it acceable while writing the Class and for later inheritance

  /**
   * Gives the sum of the given Numbers
   * @param {Number} a The first Number
   * @param {Number} b The second Number
   * @return {Number} The sum of the Numbers
   */
  sum(a, b) {
    this._WARNING('sum(a, b)');
  }
}

// and another custom interface
class MyCustomInterface2 {
  /**
   * Gives the square of the given Number
   * @param {Number} a The Number
   * @return {Number} The square of the Numbers
   */
  square(a) {
    this._WARNING('square(a)');
  }
}

// Extend your custom class even more and implement the custom interfaces
class AllInterfacesImplemented extends implement(MyCustomClass1, MyCustomInterface1, MyCustomInterface2) {
  /**
   * @inheritdoc
   */
  sum(a, b) {
    return a + b;
  }

  /**
   * Multiplies two Numbers
   * @param {Number} a The first Number
   * @param {Number} b The second Number
   * @return {Number}
   */
  multiply(a, b) {
    return a * b;
  }
}

// TEST IT

let x = new AllInterfacesImplemented();

console.log("x.foo() =", x.foo());
//output: 'x.foo() = 66'

console.log("x.square(2) =", x.square(2));
// output: 'x.square(2) = undefined
// console warn: 'WARNING! Function "square(a)" is not overridden in AllInterfacesImplemented'

console.log("x.sum(1, 2) =", x.sum(1, 2));
// output: 'x.sum(1, 2) = 3'

console.log("x.multiply(4, 5) =", x.multiply(4, 5));
// output: 'x.multiply(4, 5) = 20'

原文由 Kai Lehmann 发布，翻译遵循 CC BY-SA 4.0 许可协议