JavaScript 装饰器模式详解：从原理到实战应用

def decorator(f):
  print "my decorator"
  return f
@decorator
def myfunc():
  print "my function"
myfunc()
# my decorator
# my function

def decorator(f):
  def wrapper():
    print "my decorator"
    return f()
  return wrapper
def myfunc():
  print "my function"
myfunc = decorator(myfuc)

Object.defineProperty(obj, prop, descriptor)

@testable
class MyTestableClass {
 // ...
}

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

MyTestableClass.isTestable // true

@decorator
class A {}

// 等同于

class A {}
A = decorator(A) || A;

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

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

@testable(false)
class MyClass {}
MyClass.isTestable // false

// mixins.js
export function mixins(...list) {
 return function (target) {
  Object.assign(target.prototype, ...list)
 }
}

// main.js
import { mixins } from './mixins'

const Foo = {
 foo() { console.log('foo') }
};

@mixins(Foo)
class MyClass {}

let obj = new MyClass();
obj.foo() // 'foo'

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

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;
}

readonly(Person.prototype, 'name', descriptor);
// 类似于
Object.defineProperty(Person.prototype, 'name', descriptor);

function doSomething(name) {
 console.log('Hello, ' + name);
}

function loggingDecorator(wrapped) {
 return function() {
  console.log('Starting');
  const result = wrapped.apply(this, arguments);
  console.log('Finished');
  return result;
 }
}

const wrapped = loggingDecorator(doSomething);

import { override } from 'core-decorators';

class Parent {
 speak(first, second) {}
}

class Child extends Parent {
 @override
 speak() {}
 // SyntaxError: Child#speak() does not properly override Parent#speak(first, second)
}

// or

class Child extends Parent {
 @override
 speaks() {}
 // SyntaxError: No descriptor matching Child#speaks() was found on the prototype chain.
 //
 //  Did you mean "speak"?
}

import { deprecate } from 'core-decorators';

class Person {
 @deprecate
 facepalm() {}

 @deprecate('We stopped facepalming')
 facepalmHard() {}

 @deprecate('We stopped facepalming', { url: 'http://knowyourmeme.com/memes/facepalm' })
 facepalmHarder() {}
}

let person = new Person();

person.facepalm();
// DEPRECATION Person#facepalm: This function will be removed in future versions.

person.facepalmHard();
// DEPRECATION Person#facepalmHard: We stopped facepalming

person.facepalmHarder();
// DEPRECATION Person#facepalmHarder: We stopped facepalming
//
//   See http://knowyourmeme.com/memes/facepalm for more details.
//

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

@connect(mapStateToProps, mapDispatchToProps)
export default class MyReactComponent extends React.Component {}

/**
 * @description 在点击时，如果有新功能提醒，则弹窗显示
 * @param code 新功能的code
 * @returns {function(*, *, *)}
 */
 const checkRecommandFunc = (code) => (target, property, descriptor) => {
  let desF = descriptor.value; 
  descriptor.value = function (...args) {
   let recommandFuncModalData = SYSTEM.recommandFuncCodeMap[code];

   if (recommandFuncModalData && recommandFuncModalData.id) {
    setTimeout(() => {
     this.props.dispatch({type: 'global/setRecommandFuncModalData', recommandFuncModalData});
    }, 1000);
   }
   desF.apply(this, args);
  };
  return descriptor;
 };

@autobind
@loadingWrap(true)
async handleSelect(params) {
 await this.props.dispatch({
  type: 'product_list/setQuerypParams',
  querypParams: params
 });
}

export function loadingWrap(needHide) {

 const defaultLoading = (
  <div className="toast-loading">
   <Loading className="loading-icon"/>
   <div>加载中...</div>
  </div>
 );

 return function (target, property, descriptor) {
  const raw = descriptor.value;
  
  descriptor.value = function (...args) {
   Toast.info(text || defaultLoading, 0, null, true);
   const res = raw.apply(this, args);
   
   if (needHide) {
    if (get('finally')(res)) {
     res.finally(() => {
      Toast.hide();
     });
    } else {
     Toast.hide();
    }
   }
  };
  return descriptor;
 };
}