图像上的事件监听器不会改变无序列表的显示状态

Question

当用户点击页面右上角的菜单栏<img>时，<ul>显示属性应从none更改为display: block，反之亦然。我有图像的全局变量（监听点击）和ul（选择显示属性）。

＆＃13;

＆＃13;

var menuButton = document.getElementById("menuicon");
        var menu = document.getElementById("navlink");


      function menuclick(){
        if (menu.style.display == none){
          menu.style.display = "block";
        }
        else {
          menu.style.display = "none";
        }
      }

      menuButton.addEventListener("click", menuclick);

＆＃13;

body {
	background-color: rgb(40, 40, 40);
	font-size: 16px;
	margin: 0 auto;
	font-family: helvetica, arial;}



    header {
	position: relative;
	background: linear-gradient(rgb(40, 40, 140), rgb(50,50,180));
	min-height: 40px;
	box-shadow: 0px 0px 5px black inset;}

    header h1 {
	position: relative;
	padding: 10px;
	font-style: italic;
	font-size: 1.2em;
	font-weight: bold;
	color: white;}

    #h1s {
	font-size: .6em;}

    img {
	position: absolute;
	top: 0px;
        right: 10px;}

    header ul {
	position: relative;
	display: none;}

    header ul li {
	background-color: red;
	text-align: center;
	height: 20px;
	background-color: grey;
	box-shadow: 0px 0px 1px black inset;}

    header ul li a {
     text-decoration: none;
     color: white;
     line-height: 20px;
     font-size: .6em;}

＆＃13;

<div id="page">

      <header>
        <h1> Cole Pratt <span id="h1s"> No.2968615 </span> </h1>
        <img src="images/menuicon.png" alt="menuicon" width="40" id="menuicon"/>
        <ul id="navlink">
          <li><a href="#">home</a></li>
          <li><a href="#">about</a></li>
          <li><a href="#">bio</a></li>
        </ul>
      </header>

    </div>

＆＃13;

＆＃13;

＆＃13;

Answer 1

您可以使用 setAttribute() 为您完成工作。并且您忘记将 'none' 放在单引号中。

var menuButton = document.getElementById("menuicon");
var menu = document.getElementById("navlink");


function menuclick() {
  if (menu.style.display === 'none') {
    menu.setAttribute("style", "display:block");
  } else {
    menu.setAttribute("style", "display:none");
  }
}

menuButton.addEventListener("click", menuclick);

Answer 2

我建议您使用 css class 来显示/隐藏菜单项，而不是使用 inline styles。见Element.classList.toggle：

var menuButton = document.getElementById("menuicon");
var menu = document.getElementById("navlink");


function menuclick() {
  menu.classList.toggle("active");
}

menuButton.addEventListener("click", menuclick);

body {
  background-color: rgb(40, 40, 40);
  font-size: 16px;
  margin: 0 auto;
  font-family: helvetica, arial;
}

header {
  position: relative;
  background: linear-gradient(rgb(40, 40, 140), rgb(50, 50, 180));
  min-height: 40px;
  box-shadow: 0px 0px 5px black inset;
}

header h1 {
  position: relative;
  padding: 10px;
  font-style: italic;
  font-size: 1.2em;
  font-weight: bold;
  color: white;
}

#h1s {
  font-size: .6em;
}

img {
  position: absolute;
  top: 0px;
  right: 10px;
}

header ul {
  position: relative;
  display: none;
}

header ul.active {
  display: block;
}

header ul li {
  background-color: red;
  text-align: center;
  height: 20px;
  background-color: grey;
  box-shadow: 0px 0px 1px black inset;
}

header ul li a {
  text-decoration: none;
  color: white;
  line-height: 20px;
  font-size: .6em;
}

<div id="page">

  <header>
    <h1> Cole Pratt <span id="h1s"> No.2968615 </span> </h1>
    <img src="images/menuicon.png" alt="menuicon" width="40" id="menuicon" />
    <ul id="navlink">
      <li><a href="#">home</a></li>
      <li><a href="#">about</a></li>
      <li><a href="#">bio</a></li>
    </ul>
  </header>

</div>