Decorator 装饰器模式

Posted on In

e.g.

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let worker = {
  someMethod() {
    return 1
  },

  slow(x) {
    console.log("called with " + x)
    return x * this.someMethod()
  },
}

function decorator(func) {
  const cache = new Map()

  return function (x) {
    if (cache.has(x)) {
      console.log("cache hit")
      return cache.get(x)
    }

    const result = func.call(this, x)
    cache.set(x, result)

    return result
  }
}

worker.slow = decorator(worker.slow)

console.log(worker.slow(2))
console.log(worker.slow(2))

Injection

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function injection(func, ...argsBound) {
  return function (...args) {
    return func.call(this, ...argsBound, ...args)
  }
}

// usage
let user = {
  firstName: "Edward",
  say(time, phrase) {
    console.log(`[${time}]: ${this.firstName} ${phrase}`)
  },
}

user.say = injection(
  user.say,
  new Date().getHours() + ":" + new Date().getMinutes()
)

user.say("Hi")

arrow function

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function defer(f, ms) {
  return function () {
    setTimeout(() => f.apply(this, arguments), ms)
  }
}

function sayHello(name) {
  console.log(`Hi, ${name}`)
}

const deferSay = defer(sayHello, 2000)
deferSay("Edward")

prototype

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let user = {
  name: "Edward",
  hello(name) {
    console.log(`hi ${this.name}, this is ${name}`)
  },
}

Function.prototype.defer = function (ms) {
  let f = this
  return function (...arg) {
    setTimeout(() => f.apply(this, arg), ms)
  }
}

user.hello = user.hello.defer(1000)
user.hello("Ejklfj")