详解如何在JavaScript中使用装饰器

npm install --save-dev @babel/plugin-proposal-decorators

import { defineConfig } from 'vite';
import babel from 'vite-plugin-babel';

export default defineConfig({
    plugins: [
        babelDev({
            babelConfig: {
                plugin: ['@babel/plugin-proposal-decorators']
            }
        }),
        // ...
    ],

    // ...
})

module: {
  rules: [
    {
      test: /\.(js|mjs|jsx|ts|tsx)$/,
      use: {
        loader: 'babel-loader',
        options: {
          // ... 
          plugins: [
            ['@babel/plugin-proposal-decorators', { 'legacy': true }],
            // ...
          ],
          // ...
        },
      }
      // ...
    }
  ]
}  

@frozen
class Foo {
  @throttle(500)
  expensiveMethod() {}
}

function testable(target) {
  target.isTestable = true;
}

@testable
class MyTestableClass {
  // ...
}
MyTestableClass.isTestable // true

function testable(isTestable) {
  return function(target) {
    target.isTestable = isTestable;
  }
}
@testable(true)
class MyTestableClass {}
MyTestableClass.isTestable // true
@testable(false)
class MyClass {}
MyClass.isTestable // false

function readonly(target, name, descriptor){
  // descriptor对象原来的值如下
  // {
  //   value: specifiedFunction,
  //   enumerable: false,
  //   configurable: true,
  //   writable: true
  // };
  descriptor.writable = false;
  return descriptor;
}

class Person {
  @readonly
  name() { return `${this.first} ${this.last}` }
}

function dec(id){
  console.log('evaluated', id);
  return (target, property, descriptor) => console.log('executed', id);
}
class Example {
    @dec(1)
    @dec(2)
    method(){}
}
// evaluated 1
// evaluated 2
// executed 2
// executed 1

class Page {
	@delay(2000)
	onClick(a) {
    console.log("onClick");
  }
}

function delay(time) {
  return function (target, key, descriptor) {
    const oldFunction = descriptor.value;
    descriptor.value = function() {
      setTimeout(() => {
        oldFunction.apply(this, arguments);
      }, time);
    }
    return descriptor;
  }
}

class Page {
	@throttle(2000)
	onClick(a) {
    console.log("onClick");
  }
}

function throttle(time) {
  return function (target, key, descriptor) {
    const oldFunction = descriptor.value;
    let isLock = false;
    descriptor.value = function() {
      if(isLock) { return; }
     	isLock = true;
      oldFunction.apply(this, arguments);
      setTimeout(() => {
        isLock = false; 
      }, time);
    }
    return descriptor;
  }
}

class Page {
	@debounce(2000)
	onClick(a) {
    console.log("onClick");
  }
}

function debounce(time) {
  return function (target, key, descriptor) {
    const oldFunction = descriptor.value;
    let timer = null;
    descriptor.value = function () {
      clearTimeout(timer);
      timer = setTimeout(() => {
        oldFunction.apply(this, arguments)
      }, time);
    };
    return descriptor;
  }
}