正确扩展ES6中的数组/代理? [英] Extending Array / Proxy in ES6 correctly?

问题描述

当前正在尝试自定义实现Array/Object(我想最终会变得非常相似)，并且偶然发现了一个令我抓狂的问题.

Currently trying to make a custom implementation of Array / Object (Would end up being pretty similar i suppose) and have stumbled upon an issue that is driving me crazy.

如您所见，b只是一个instanceOf Array，即使它是从自定义类CachedArray创建的，也因此未定义我的自定义函数testPush，因此我无法为所有问题找到问题所在.

As you can see, b is only an instanceOf Array, even though its created from custom class CachedArray, thus my custom function testPush is not defined, and i cant for the sake of everything find what is the issue.

使用Nodejs 6

Using Nodejs 6

function _setKey(target, key, value) {
  console.log('Setting value', key, 'to', value);
  target[key] = value;
  return true;
}

class ExtendableProxy {
  constructor(a, b) {
    return new Proxy(a, b);
  }
}

class CachedArray extends ExtendableProxy {
  constructor(redis, options) {
    let RawArray = [];

    super(RawArray, {
      set: _setKey
    });

    this._rawArray = RawArray;

    this.redis = redis;
    this.options = options;
  }

  testPush() {
    this.push('Its me');
  }
}

var b = new CachedArray();

console.log('b instanceof CachedArray', b instanceof CachedArray); //false
console.log('b instanceof ExtendableProxy', b instanceof ExtendableProxy); //false
console.log('b instanceof Proxy', b instanceof Proxy); //false
console.log('b instanceof Array', b instanceof Array); //true

b.push('Hello.'); //Works just fine, _setKey is called and executed correctly
b.testPush(); //TypeError: b.testPush is not a function

推荐答案

除了我要实现的目标之外，还有其他选择吗?本质上，我需要一个具有我的一些附加功能的数组，但是该数组具有与之连接的代理，以便我可以进一步处理对类实例(即数组)发生的任何写操作

Is there an alternative to what i am trying to achieve? Essentially i need an array with some extra functions of mine, which however has a Proxy connected to it, so that i can further process any writes happening to the instance of my class (So, the Array)

嗯，代理服务器有一个处理程序，使您可以与代理对象进行各种交互.因此，您应该使用该方法注入要添加到代理对象的任何其他方法.例如，只需提供 get ，以便它返回自定义函数，而不是将调用中继回目标:

Well, the proxy has a handler that allows you to hook into every kind of interaction with the proxied object. So you should use that to inject any additional methods you want to add to the proxied object. For example, just provide the get so it returns a custom function instead of relaying the call back to the target:

function createCachedArray(arr) {
    const customFunctions = {
        testPush() {
            this.push('It’s me');
        },
    };

    return new Proxy(arr, {
        set (target, property, value) {
            console.log(`Setting value ${property} to ${value}`);
            target[property] = value;
            return true;
        },
        has (target, property) {
            return property in customFunctions || property in target;
        },
        get (target, property) {
            if (typeof property === 'string' && property in customFunctions) {
                return customFunctions[property].bind(target);
            }
            else {
                return target[property];
            }
        },
    });
}

let a = [1, 2, 3];
let b = createCachedArray(a);

b.push('foo');
b.testPush();
for (const x of b) {
    console.log(x);
}

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