一文理解JavaScript装饰器模式

装饰器代码示例

const log = (srcFun) => {
if(typeof(srcFun) !== 'function') {
throw new Error(`the param must be a function`);
}
return (...arguments) => {
console.info(`${srcFun.name} invoke with ${arguments.join(',')}`);
srcFun(...arguments);
}
}
const plus = (a, b) => a + b;
const logPlus = log(plus);
logPlus(1,2);
// plus invoke with 1,2

const log = (target, name, descriptor) => {
var oldValue = descriptor.value;
descriptor.value = function() {
console.log(`Calling ${name} with`, arguments);
return oldValue.apply(this, arguments);
};
return descriptor;
}
class Math {
@log // Decorator
plus(a, b) {
return a + b;
}
}
const math = new Math();
math.plus(1, 2);
// Calling plus with 1,2

// readonly 装饰器
import { readonly } from 'core-decorators';
class Fudao {
@readonly
title = 'A';
}
var fudao = new Fudao();
fudao.title = 'B'; // This will log error & doesn't work