装饰器模式实现数据埋点

log.js

Function.prototype.after = function(afterFn) {
  const __this = this;
  return function() {
    const ret = __this.apply(this, arguments);
    afterFn.apply(this, arguments);
    return ret;
  }
}

let showLogin = function() {
  console.log('打开登录框');
}

const log = function() {
  console.log(`上报标签：${this.getAttribute('tag')}`);
  // (new Image).src = 'https://xxx.com'// 上报给后端接口
}

showLogin = showLogin.after(log);
document.getElementById('button').onclick = showLogin;