使用addEventlistener只需两次单击即可使用按钮

Question

一直试图找到让我的菜单按钮只需点击一下即可工作的方法，但只有当你点击它两次时它才有效。该按钮使菜单的不透明度从0变为1，因此它将在右上方缓慢弹出。任何人提供任何想法如何解决我遇到的这个问题。我知道在菜单栏重新出现之前会先调用某些内容，但不确定是哪一个，我尝试了其他一些替代方案。

function toggleMenu() {
  var x = document.getElementById("navi");
  if (x.style.opacity === "0") {
    x.style.opacity = "1";
    x.classList.add("navigation");
  } else {
    x.style.opacity = "0";
  }


};
window.onload = function() {
  var click = document.getElementById("menuToggle")
  click.addEventListener("click", toggleMenu);
};

* {
  margin: 0;
  padding: 0;
}

html,
body {
  margin: 0;
  padding: 0;
  overflow-x: hidden;
  height: 100%;
}


/* first menu */

#navi {
  opacity: 0;
  text-align: center;
  height: 40px;
  width: -50%;
  z-index: 1;
  transition: all 3s ease;
}

#navi li {
  float: right;
  display: inline;
  color: white;
  margin: 20px;
  padding: 15px;
  width: 100px;
  background-color: rgba(194, 147, 129, .7);
  font-family: 'Cabin', sans-serif;
  cursor: pointer;
}

#navi.navigation {
  opacity: 1;
  height: 40px;
}


/* second menu */

#title {
  padding-top: 50px;
  position: relative;
}

#title li {
  display: inline-block;
  color: red;
  margin: 50px;
}

#title li button {
  padding: 10px;
  width: 100px;
  border: 2px solid #F5ECE1;
  background-color: #C29381;
  color: white;
  cursor: pointer;
  font-family: 'Cabin', sans-serif;
}

#title li button:hover,
#nav li:hover {
  background-color: rgba(166, 99, 72, .7);
}

#demo {
  text-align: center;
  font-size: 60px;
  padding-bottom: 50px;
}

.parallax {
  background-image: url(img/beans.jpg);
  width: 100%;
  min-height: 100%;
}

.parallax {
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center;
  position: relative;
  z-index: 0;
}

.textBox {
  position: absolute;
  top: 50%;
  width: 100%;
  text-align: center;
  font-size: 30px;
  color: white;
  font-family: 'Cabin', sans-serif;
}

.textBox h1 {
  position: absolute;
  bottom: 150%;
  text-align: center;
  width: 100%;
  font-size: 300%;
}

.textBox .border {
  background-color: #C86428;
  color: #fff;
  padding: 20px;
}

.textBox .border.trans {
  background-color: transparent;
  font-size: 40px;
}

.contact-icon {
  width: 5%;
  opacity: 0;
  transition: all 3s ease;
}

.contact-icon img {
  width: 4%;
  margin: 10px;
}

.contact-icon.iToggle {
  opacity: 1;
  width: 100%;
}

<div class="parallax">
  <ul id="navi">
    <li>Recipe</li>
    <li>Experiment</li>
    <li>About</li>
  </ul>
  <div class="textBox">
    <h1>Mad Monks Brewing Co</h1>
    <p id="demo"></p>
    <span class="border">
          Coming Soon
        </span>

    <ul id="title">
      <li>
        <button id="menuToggle">Menu</button></li>
      <li>
        <button onclick="iconToggle()">Contact</button>
      </li>
    </ul>

    <section id="social-icon" class="contact-icon">
      <img src="img/facebook.png">
      <img src="img/instagram.png">
      <img src="img/twitter.png">
    </section>
  </div>
</div>

Answer 1

问题是，在页面加载时，有问题的元素没有opacity属性;它不是0或1，它是空白的（空字符串）。通过将其转换为真实性测试来修复它，这将适用于空白值和"0"：

if (!x.style.opacity) {

像

＆＃13;

＆＃13;

function toggleMenu() {
  var x = document.getElementById("navi");
  if (!x.style.opacity) {
    x.style.opacity = "1";
    x.classList.add("navigation");
  } else {
    x.style.opacity = "0";
  }
}
window.onload = function() {
  var click = document.getElementById("menuToggle")
  click.addEventListener("click", toggleMenu);
};

＆＃13;

* {
  margin: 0;
  padding: 0;
}

html,
body {
  margin: 0;
  padding: 0;
  overflow-x: hidden;
  height: 100%;
}

/* first menu */

#navi {
  opacity: 0;
  text-align: center;
  height: 40px;
  width: -50%;
  z-index: 1;
  transition: all 3s ease;
}

#navi li {
  float: right;
  display: inline;
  color: white;
  margin: 20px;
  padding: 15px;
  width: 100px;
  background-color: rgba(194, 147, 129, .7);
  font-family: 'Cabin', sans-serif;
  cursor: pointer;
}

#navi.navigation {
  opacity: 1;
  height: 40px;
}

/* second menu */

#title {
  padding-top: 50px;
  position: relative;
}

#title li {
  display: inline-block;
  color: red;
  margin: 50px;
}

#title li button {
  padding: 10px;
  width: 100px;
  border: 2px solid #F5ECE1;
  background-color: #C29381;
  color: white;
  cursor: pointer;
  font-family: 'Cabin', sans-serif;
}

#title li button:hover,
#nav li:hover {
  background-color: rgba(166, 99, 72, .7);
}

#demo {
  text-align: center;
  font-size: 60px;
  padding-bottom: 50px;
}

.parallax {
  background-image: url(img/beans.jpg);
  width: 100%;
  min-height: 100%;
}

.parallax {
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center;
  position: relative;
  z-index: 0;
}

.textBox {
  position: absolute;
  top: 50%;
  width: 100%;
  text-align: center;
  font-size: 30px;
  color: white;
  font-family: 'Cabin', sans-serif;
}

.textBox h1 {
  position: absolute;
  bottom: 150%;
  text-align: center;
  width: 100%;
  font-size: 300%;
}

.textBox .border {
  background-color: #C86428;
  color: #fff;
  padding: 20px;
}

.textBox .border.trans {
  background-color: transparent;
  font-size: 40px;
}

.contact-icon {
  width: 5%;
  opacity: 0;
  transition: all 3s ease;
}

.contact-icon img {
  width: 4%;
  margin: 10px;
}

.contact-icon.iToggle {
  opacity: 1;
  width: 100%;
}

＆＃13;

<div class="parallax">
  <ul id="navi">
    <li>Recipe</li>
    <li>Experiment</li>
    <li>About</li>
  </ul>
  <div class="textBox">
    <h1>Mad Monks Brewing Co</h1>
    <p id="demo"></p>
    <span class="border">
          Coming Soon
        </span>

    <ul id="title">
      <li>
        <button id="menuToggle">Menu</button></li>
      <li>
        <button onclick="iconToggle()">Contact</button>
      </li>
    </ul>

    <section id="social-icon" class="contact-icon">
      <img src="img/facebook.png">
      <img src="img/instagram.png">
      <img src="img/twitter.png">
    </section>
  </div>
</div>

＆＃13;

＆＃13;

＆＃13;