javascript - 如何制作数字轮循环？

Question

我有一个从 0 到 9 的随机数轮。轮子向下或向上旋转以落在随机数上。我怎样才能使轮子只旋转下来？ (一旦它达到 9，下一个数字是 0、1、2...9、0、1、2)而不必有很多 div。

function roll() {
  var randomNum = Number((Math.random() * 100).toFixed(2));
  var firstDigit = Number(Math.floor((randomNum) / 10 - 5));
  var win = firstDigit;
  if (win > 4) {
    var rollm = win * 40 - 40 * 15;
    document.getElementById("roll").style = "margin-top: " + rollm + "px ";
  }
  if (win < 4) {
    var rollm = 180 - 40 * win - 380;
    document.getElementById("roll").style = "margin-top: " + rollm + "px ";
  }
  if (win == 4) {
    var rollm = 360;
    document.getElementById("roll").style = "margin-top: -" + rollm + "px ";
  }
}

body {
  color: #fff;
}
#roll {
  transition: .5s ease;
}
.ticker {
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 15px 0px 15px 26px;
  border-color: transparent #fff transparent;
  margin: 0 -20px;
  transform: translateY(-75px);
}
#roll {
  width: 40px;
  height: 360px;
  background: #0077ee;
  margin: 0 auto;
}
.roll-h {
  width: 40px;
  height: 120px;
  margin: 0 auto;
  overflow: hidden;
}
.shadow {
  height: 40px;
  margin: 0 auto;
  transform: translateY(40px);
}
.black,
.his-h {
  width: 40px;
  height: 40px;
  font-size: 20px;
  line-height: 40px;
  font-weight: 700;
  text-align: center;
  float: left;
}
.black {
  background: black;
}
.floatleft {
  float: left;
}

<div style="margin:0 auto; display:inline-block">
  <div class="shadow"></div>
  <div class="roll-h">
    <div id="roll">
      <div class="black">9</div>
      <div class="black">0</div>
      <div class="black">1</div>
      <div class="black">2</div>
      <div class="black">3</div>
      <div class="black">4</div>
      <div class="black">5</div>
      <div class="black">6</div>
      <div class="black">7</div>
      <div class="black">8</div>
      <div class="black">9</div>
      <div class="black">0</div>
    </div>
  </div>
  <div class="ticker"></div>
</div>
<button onClick="roll()" id="spin">Spin</button>

Answer 1

我稍微修改了您的代码段以实现您要求的行为。

但是有两个问题。首先，您将需要几乎两倍的 div 来正确地设置动画。其次，transitionend事件是not supported in all browsers , 有时它需要加上前缀，所以如果你关心支持 IE < 10 之类的东西，那么开箱即用它不适合你。

编辑

如 the other answer 中所述您可以考虑仅在单击按钮时重置“滚轮”位置，而不是使用 transitionend 事件。这很好，但它需要更复杂的实现，因为您需要记住(以某种方式)您需要重置到哪个位置。

function roll() {
  var win = Math.floor(Math.random() * 10);
  var roll = document.getElementById("roll");
  var onTransitionend = function () {
    roll.classList.remove("animated");
    roll.style = "margin-top: " + (- win * 40) + "px ";
    roll.removeEventListener("transitionend", onTransitionend);
  };
  roll.classList.add("animated");
  roll.style = "margin-top: " + (- win * 40 - 400) + "px ";
  roll.addEventListener("transitionend", onTransitionend);
}

body {
  color: #fff;
}
#roll.animated {
  transition: .5s ease;
}
.ticker {
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 15px 0px 15px 26px;
  border-color: transparent #fff transparent;
  margin: 0 -20px;
  transform: translateY(-75px);
}
#roll {
  width: 40px;
  // height: 360px;
  background: #0077ee;
  margin: 0 auto;
}
.roll-h {
  width: 40px;
  height: 120px;
  margin: 0 auto;
  overflow: hidden;
}
.shadow {
  height: 40px;
  margin: 0 auto;
  transform: translateY(40px);
}
.black,
.his-h {
  width: 40px;
  height: 40px;
  font-size: 20px;
  line-height: 40px;
  font-weight: 700;
  text-align: center;
  float: left;
}
.black {
  background: black;
}
.floatleft {
  float: left;
}

<div style="margin:0 auto; display:inline-block">
  <div class="shadow"></div>
  <div class="roll-h">
    <div id="roll">
      <div class="black">9</div>
      <div class="black">0</div>
      <div class="black">1</div>
      <div class="black">2</div>
      <div class="black">3</div>
      <div class="black">4</div>
      <div class="black">5</div>
      <div class="black">6</div>
      <div class="black">7</div>
      <div class="black">8</div>
      <div class="black">9</div>
      <div class="black">0</div>
      <div class="black">1</div>
      <div class="black">2</div>
      <div class="black">3</div>
      <div class="black">4</div>
      <div class="black">5</div>
      <div class="black">6</div>
      <div class="black">7</div>
      <div class="black">8</div>
      <div class="black">9</div>
      <div class="black">0</div>
    </div>
  </div>
  <div class="ticker"></div>
</div>
<button onClick="roll()" id="spin">Spin</button>