javascript - 在多个进度条动画中将每个进度条从 0 加载到其值

Question

我正在尝试在分组进度条中添加动画，该动画会将每个进度条从 0 加载到其值。例如，在下面的示例代码中，我想首先加载红色进度条，然后加载绿色进度条。我怎样才能做到这一点？

请检查this jsfiddle中的代码.

html:

<div class="progress-bar-outer">
  <div class="progress-bar-inner">
  </div>
  <div class="progress-bar-inner2">
  </div>
</div>

CSS:

.progress-bar-outer {
  width: 300px;
  height: 40px;
  flex: auto;
  display: flex;
  flex-direction: row;
  border-radius: 0.5em;
  overflow: hidden;
  background-color: gray;
}
.progress-bar-inner {
  /* You can change the `width` to change the amount of progress. */
  width: 75%;
  height: 100%;
  background-color: red;
}
.progress-bar-inner2 {
  /* You can change the `width` to change the amount of progress. */
  width: 50%;
  height: 100%;
  background-color: green;
}

.progress-bar-outer div {
      animation:loadbar 3s;
    -webkit-animation:loadbar 3s;
}

@keyframes loadbar {
    0% {width: 0%;left:0;right:0}
}

Answer 1

为了获得更好的性能，我会转换transform。使用 translateX(-100%) 和 opacity: 0 将它们移动到默认的隐藏位置，然后设置动画到 translateX(0)； opacity: 1; 将它们放置到位。只需将 animation-delay 添加到与 animation-duration

匹配的绿色条即可

我将条形设置为半透明，以便在动画触发时显示。

.progress-bar-outer {
  width: 300px;
  height: 40px;
  border-radius: 0.5em;
  overflow: hidden;
  background-color: gray;
  display: flex;
}

.progress-bar-inner {
  /* You can change the `width` to change the amount of progress. */
  width: 75%;
  background-color: red;
}

.progress-bar-inner2 {
  /* You can change the `width` to change the amount of progress. */
  width: 100%;
  background-color: green;
}

.progress-bar-outer div {
  transform: translateX(-100%);
  animation: loadbar 3s forwards;
  -webkit-animation: loadbar 3s forwards;
  opacity: 0;
}

.progress-bar-outer .progress-bar-inner2 {
  animation-delay: 3s;
}

@keyframes loadbar {
  0% {
    opacity: 1;
  }
  100% {
    transform: translateX(0);
    opacity: 1;
  }
}

<!-- Learn about this code on MDN: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/progress -->

<div class="progress-bar-outer">
  <div class="progress-bar-inner">
  </div>
  <div class="progress-bar-inner2">
  </div>
</div>