How to use Proxy to simulate PHP's __callStatic attribute in Node.js

Question

I'm trying to create the same behavior in Node.js as the PHP __callStatic magic method.

I'm trying to do it using Proxy but I'm not sure if it's the best option.

<code>class Test {
  constructor() {
    this.num = 0
  }
  
  set(num) {
    this.num = this.num num

    return this
  }
  
  get() {
    return this.num
  }
}

const TestFacade = new Proxy({}, {
  get: (_, key) => {
    const test = new Test()
        
    return test[key]
  }
})


//The execution method chain ends with get
console.log(TestFacade.set(10).set(20).get())
//Expected result: 30
//Return result: 0

// Start a new execution method chain and instantiate the Test class again in the first set
console.log(TestFacade.set(20).set(20).get())
//Expected result: 40
// Return result: 0</code>

The problem is that every time I try to access the properties of TestFacade, the get trap is triggered. The behavior I need is that when the set method is called it will return this of the Test class and I can even save that instance for later use!

const testInstance = TestFacade.set(10) // The set method returns `this` of `Test` instead of Proxy

If anything is unclear, please let me know.

Answer 1

I don't know if this is the best option. But I solved the problem by returning a new proxy in the get trap that binds the test class instance into the method using the apply trap ：

class Facade {
  static #facadeAccessor

  static createFacadeFor(provider) {
    this.#facadeAccessor = provider

    return new Proxy(this, { get: this.__callStatic.bind(this) })
  }

  static __callStatic(facade, key) {
    /**
     * 访问Facade类的方法而不是提供者的方法。
     */
    if (facade[key]) {
      return facade[key]
    }

    const provider = new this.#facadeAccessor()

    const apply = (method, _this, args) => method.bind(provider)(...args)

    if (provider[key] === undefined) {
      return undefined
    }

    /**
     * 访问类的属性。
     */
    if (typeof provider[key] !== 'function') {
      return provider[key]
    }

    return new Proxy(provider[key], { apply })
  }
}

class Test {
  num = 0

  set(num) {
    this.num = this.num + num

    return this
  }

  get() {
    return this.num
  }
}

const TestFacade = Facade.createFacadeFor(Test)

console.log(TestFacade.set(10).set(20).get()) // 30
console.log(TestFacade.set(5).set(5).get()) // 10

const testInstance = TestFacade.set(10)

console.log(testInstance.num) // 10
console.log(testInstance.get()) // 10
console.log(testInstance.set(10).get()) // 20