javascript - 切换函数在 transitionend 上触发两次

Question

我有一个切换器，我正在使用 jQuery 调用其 checked 状态。每次我单击从未选中切换到选中时，控制台都会记录 “do this!” 两次。为什么此函数会触发两次？让它触发一次的解决方法是什么？

$("#my-toggle").bind("transitionend webkitTransitionEnd oTransitionEnd MSTransitionEnd", function() {
  if (document.getElementById('my-checkbox').checked) {
    console.log("do this!")
  }
});

.switch {
  position: absolute;
  top: 15%;
  display: inline-block;
  width: 60px;
  height: 34px;
}

.switch input {
  display: none;
}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ccc;
  -webkit-transition: .4s;
  transition: .4s;
}

.slider:before,
.slider .number {
  position: absolute;
  content: "";
  height: 26px;
  width: 26px;
  left: 4px;
  bottom: 4px;
  background-color: white;
  -webkit-transition: .4s;
  transition: .4s;
}

.slider .number {
  background: none;
  font-size: 14px;
  left: 9px;
  top: 9px;
}

input:checked+.slider {
  background-color: #2196F3;
}

input:focus+.slider {
  box-shadow: 0 0 1px #2196F3;
}

input:checked+.slider:before,
input:checked+.slider .number {
  -webkit-transform: translateX(26px);
  -ms-transform: translateX(26px);
  transform: translateX(26px);
}


/* Rounded sliders */

.slider.round {
  border-radius: 34px;
}

.slider.round:before {
  border-radius: 50%;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
<label class="switch">
  <input type="checkbox" id="my-checkbox">
  <span class="slider round" id="my-toggle"></span>
</label>

我的最终 HTML 如下所示，为此事件触发了三次:

<label class="switch">
  <input type="checkbox" id="my-checkbox">
  <span class="slider round" id="my-toggle">
    <span class="number">00</span>
  </span>
</label>

Answer 1

有两个transitionend事件触发:一个来自你的 #my-toggle <span> , 一个来自你的 ::before伪元素。您需要区分这两个事件。你需要事件参数 e为此。

然后在 e.originalEvent.propertyName 中找到唯一的区别(对于相应的 CSS 属性)和 e.originalEvent.pseudoElement .

所以让我们检查 if 中的最后一个属性条件。

再放一个&& e.target == this在那里，因为 transitionend event is also firing for children因为事件冒泡了。因为你只听 parent 的事件 <span> , 你不能简单地调用 e.stopPropagation这只会对防止父级触发事件有用。

$("#my-toggle").bind("transitionend webkitTransitionEnd oTransitionEnd MSTransitionEnd", function(e) {
  if (document.getElementById("my-checkbox").checked && !e.originalEvent.pseudoElement && e.target == this) {
    console.log("do this!");
  }
});

.switch {
  position: absolute;
  top: 15%;
  display: inline-block;
  width: 60px;
  height: 34px;
}

.switch input {display:none;}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ccc;
  -webkit-transition: .4s;
  transition: .4s;
}

.slider:before,
.slider .number {
  position: absolute;
  content: "";
  height: 26px;
  width: 26px;
  left: 4px;
  bottom: 4px;
  background-color: white;
  -webkit-transition: .4s;
  transition: .4s;
}
.slider .number {
  background: none;
  font-size: 14px;
  left: 9px;
    top: 9px;
}

input:checked + .slider {
  background-color: #2196F3;
}

input:focus + .slider {
  box-shadow: 0 0 1px #2196F3;
}

input:checked + .slider:before,
input:checked + .slider .number {
  -webkit-transform: translateX(26px);
  -ms-transform: translateX(26px);
  transform: translateX(26px);
}

/* Rounded sliders */
.slider.round {
  border-radius: 34px;
}

.slider.round:before {
  border-radius: 50%;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<label class="switch">
  <input type="checkbox" id = "my-checkbox">
  <span class="slider round" id = "my-toggle">
     <span class="number">00</span>
  </span>
</label>