JavaScript设计模式之装饰者模式定义与应用示例

function Person() {
}
Person.prototype.sayHello = function() {
  console.log('Hello, Alice!');
};
function Decorator(param) {
  this.person = param;
}
Decorator.prototype.sayHello = function() {
  this.person.sayHello();
  console.log('Hello, Bruce!');
};
Decorator.prototype.sayGoodbye = function() {
  console.log('Bye, everyone!');
};
new Decorator(new Person()).sayHello();
/*
输出：
Hello, Alice!
Hello, Bruce!
*/
new Decorator(new Person()).sayGoodbye();
/*
输出：
Bye, everyone!
*/

var div = document.getElementById('div');
div.onclick = function() {
  console.log('First click!');
}
var decorator = function() {
  var args = arguments;
  var element = document.getElementById(args[0]);
  if (typeof element.onclick === 'function') {
    var firstClick = element.onclick;
    element.onclick = function() {
      firstClick();
      args[1]();
    }
  }
  else
    element.onclick = args[1];
}
decorator('div', function() {
  console.log('Second click!');
});
/*
输出：
First click!
Second click!
*/