text: let getSingle = function(fn) {
  	let result
  	return function() {
  		return result || (result = fn.apply(this, arguments))
  	}
  }
  
  let CreateLoginLayer = function() {
  	let div = document.createElement('div')
  	div.innerHTML = '我的登录框'
  	div.style.display = 'none'
  	document.body.appendChild(div)
  	return div
  }
  
  let createSingleLoginLayer = getSingle(CreateLoginLayer)
  
  // 创建登录框
  document.getElementById('loginBtn').onclick = function() {
  	let loginLayer = createSingleLoginLayer()
  	loginLayer.style.display = 'block'
  }
  
  // 创建一个唯一的iframe
  let CreateIframe = function() {
  	let iframe = document.createElement('iframe')
  	document.body.appendChild(iframe)
  	return iframe
  }
  
  let createSingleIfrmae = getSingle(CreateIframe)
  
  document.getElementById('loginBtn').onclick = function() {
  	let loginLayer = CreateIframe()
  	loginLayer.src = 'http://1233.com'
  }
  