详解es6超好用的语法糖Decorator

@testable
class MyClass{}

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

console.log(MyClass.isTestable) // true

var _class;

let MyClass = testable(_class = class MyClass {}) || _class;

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

@testable(false)
class MyAnotherClass{
  
}
function testable(status){
  return target=>{target.prototype.isTestable=status}
}
console.log('MyClass.isTestable',MyAnotherClass.prototype.isTestable) // false

const foo={isTestable:true}
function testable(...list){
  return target=>{Object.assign(target.prototype,...list)}
}

@testable(foo)
class MyAnotherClass{}
const obj=new MyAnotherClass()

console.log('MyClass.isTestable',obj.isTestable) // true

class MyReactComponent extends React.Component {}

export default connect(mapStateToProps, mapDispatchToProps)(MyReactComponent);

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

// target:在方法中的target指向类的prototype
function readonly(target,key,descriptor){
  descriptor.writable=false
  return descriptor
}

class MyClass{
  @readonly
  print(){console.log(`a:${this.a}`)}
}

var person = {}
Object.defineProperty(person,'name',{
  configurable:false,//能否使用delete、能否需改属性特性、或能否修改访问器属性、，false为不可重新定义，默认值为true
  enumerable:false,//对象属性是否可通过for-in循环，flase为不可循环，默认值为true
  writable:false,//对象属性是否可修改,flase为不可修改，默认值为true
  value:'xiaoming' //对象属性的默认值，默认值为undefined
});

{
   value: specifiedFunction,
   enumerable: false,
   configurable: true,
   writable: true
};

class Math{
  @log
  add(a,b){
    return a+b
  }
}

const math=new Math()
math.add(1,2)

function log(target,name,descriptor){
  const oldValue=descriptor.value

  descriptor.value=function(){
    console.log(`calling ${name} with ${JSON.stringify(arguments)}`)
    return oldValue.apply(this,arguments)
  }

  return descriptor
}

calling add with {"0":1,"1":2}

class Example {
  @readonly
  @enumable
  method(){}
}

class Example {
  @decorator(1)
  @decorator(2)
  method(){}
}

function decorator(id){
  console.log('id is ',id)
  return (target,property,descriptor)=>console.log('executed',id)
}

yarn add babel-plugin-transform-decorators-legacy babel-preset-es2017

{
  "presets": ["es2017"],
  "plugins":[
    "transform-decorators-legacy"
  ]
}

// package.json

 "scripts": {
  "build": "babel ./decorator -d lib",
  "start":"yarn build && node ./lib/index.js"
 },