装饰器模式

decorator.js

const decorator = (input, fn) => {
  const input = document.getElementById(input);
  if (typeof input.onclick === 'function') {
    const oldClickFn = input.onclick;
    input.onclick = () => {
      oldClickFn();
      fn();
    }
  } else {
    input.onclick = fn;
  }
}