ES6+:装饰器原理

[Chenjiayuan195]

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[Chenjiayuan195]

作用于类的装饰器：其实就是将当前类作为参数传入装饰器函数
作用于类属性的装饰器：调用了Object.defineProperty,如下例子

class Dog {
    @extendsArgs
    say() {
        console.log("hello");
    }
}
function extendsArgs(target,name,descriptor){
  target.name = 'Tom',
 discriptor.writable = false;
}

let Tom = new Dog();
// Tom.name = 'Tom'

Tom.say = function() {
    console.log("woof !");
}
Tom.say() // 'hello'

所以作为类属性的时候实际是如下

let descriptor = {
    value: function() {
        console.log("hello");
    },
    enumerable: false,
    configurable: true,
    writable: true
};

descriptor = readonly(Dog.prototype, "say", descriptor) || descriptor;

Object.defineProperty(Dog.prototype, "say", descriptor);