javascript - 将旧值作为 "ghost"thumb 添加到 <input type ="range"> Slider

Question

我使用 example from w3schools 设置了常规范围 slider 的样式.我的目标是向外部基于 MQTT 的智能家居发送一个新值命令，并首先将旧值显示为某种幽灵拇指:

smarthome 系统确认新值后，气泡将被移除 - 但目前这不是我的问题。我想把幽灵放在 slider 的背景和真实值拇指之间，目前它看起来像这样:

在这里你可以看到 result on JSFiddle , 这是代码:

$('#slider_1').data('last-mqtt-value', 0.5);

$('#slider_1').on('input', function() {
  // Show ghost slider
  $('#slider_1_companion').css('left', 'calc('+ $(this).data('last-mqtt-value') / $(this).attr('max') +'* (100% - 20px))');
  $('#slider_1_companion').css('display', 'block');
});

$('#slider_1').on('change', function() {
  console.log( $(this).data('last-mqtt-value'), $(this).val() );

	// Simulate new input value incoming
  ///*
  setTimeout(() => {
    $(this).data('last-mqtt-value', $(this).val());
    $('#slider_1_companion').css('display', 'none');
  },5000);
  // */
});

.slider {
    -webkit-appearance: none;
    width: 100%;
    height: 10px;
    border-radius: 5px;   
    background: #ccc;
    outline: none;
}

.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%; 
    background: #6c757d;
    cursor: pointer;
    z-index: 5;
}

.slider::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: #6c757d;
    cursor: pointer;
    z-index: 5;
}
/*https://stackoverflow.com/a/46318225/1997890*/
.slider_wrapper {
    position: relative;
    width: 150px;
}
.slider_companion {
    background-color: #ccc;
    border-radius: 50%;
    width: 20px;
    height: 20px;
    position: absolute;
    top: calc(100% - 19px); /* for some reason this is not 20px (height of thumb) */
    /* left: calc( PERCENTAGE * (100% - 20px)); /* add this line dynamically via jQuery */
    display: none;
    pointer-events: none; /*click-through*/
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div id="slider_1_wrapper" class="slider_wrapper">
  <div id="slider_1_companion" class="slider_companion"></div>
  <input type="range" id="slider_1" class="slider" min="0" max="1.0" step="any">
</div>

Answer 1

我会考虑为 slider 使用 box-shadow，您可以使用 CSS 变量进行调整，无需额外的元素，您将获得预期的结果。

这是一个想法:

$('#slider_1').data('last-mqtt-value', 0.5);

$('#slider_1').on('input', function() {
  document.getElementById('slider_1_wrapper').style.setProperty("--c", 
  ($(this).data('last-mqtt-value') -  $(this).val() )*130 + 'px');
  /*130 = 150 - 20 = width of wrapper - width of thumb*/
  
});

$('#slider_1').on('change', function() {
   console.log( $(this).data('last-mqtt-value'), $(this).val() );

	// Simulate new input value incoming
  ///*
  setTimeout(() => {
    $(this).data('last-mqtt-value', $(this).val());
    document.getElementById('slider_1_wrapper').style.setProperty("--c",0);
  },5000);
  // */
});

.slider {
    -webkit-appearance: none;
    width: 100%;
    height: 10px;
    border-radius: 5px;   
    background: #ccc;
    outline: none;
}

.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%; 
    background: #6c757d;
    cursor: pointer;
    z-index: 5;
    box-shadow:var(--c,0) 0 0 red;
}

.slider::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: #6c757d;
    cursor: pointer;
    z-index: 5;
    box-shadow:var(--c,0) 0 0 red;
}
.slider_wrapper {
    width: 150px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div id="slider_1_wrapper" class="slider_wrapper">
  <input type="range" id="slider_1" class="slider" min="0" max="1.0" step="any">
</div>