vue使用计算属性完成动态滑竿条制作

<div id="slider">
        <!-- 主要动画效果：字体和进度条以及表情随情绪程度百分比变化 -->
        <label for="range" :style="{'color':getHappinessColor}">情绪程度: {{val}}%</label>
<!-- 滑动杆的颜色应该与预先设置好的颜色进行绑定，颜色可随意更改 -->
        <!-- 情绪程度的值也应该随val值变动 -->
        <input type="range" name="" id="range" min="0" max="100" v-model="val">
 
<!-- 滑动杆的值应该与val绑定，val写入了计算属性,为了与下方滑动杆填充颜色的范围同步 -->
        <div class="slider outer">
 <!-- 让我们label 的宽度 等于们数据中心 val 的宽度,这样就会随着滑动杆的运动带动label 运动,达到更改表情的效果  -->
        <label for="" class="slider inner" :style="{'width':val+'%',
        'border-radius':greaterThanFifty}">
                <span :style="{'right':getPlacement}">{{getHappiness}}</span>
            </label>
        </div>
    </div>

*{
    padding: 0;
    margin: 0;
    list-style: none;
}
:root {
    
    --yellow: #ffd100;
    --orange: #ff6a13;
    --darkGray: #53565a;
    --midGray: #888b8d;
    --white: #fff;
  }
*,*::after,*::before{
    color: var(--darkGray);
    box-sizing: border-box;
}
html,body {
      width: 100%;
      height: 100%;
}
body{
      min-height: 100vh;
      display: flex;
      justify-content: center;
      align-items: center;
      background-color: var(--white);
}
#slider{
    
    --roundness: 20px;
    width: 100%;
    max-width: 600px;
    outline: 1px dashed red;
    padding: 4vh;
 
    
    display: grid;
    justify-content: stretch;
}
#slider>label{
    width: 100%;
    font-size: 1.5em;
    padding: 0 0 0.5em;
    margin: auto;
}
#slider input{
    grid-row: 2 / 3;
    grid-column: 1 / 2;
    width: 100%;
    position: relative;
    z-index: 1;
    opacity: 0;
    height: calc(var(--roundness) * 2);
    cursor: pointer;
}
#slider .outer{
    width: 100%;
    height: var(--roundness);
    background-color: var(--midGray);
    border-radius: var(--roundness);
    display: flex;
    align-items: center;
    align-content: center;
    position: relative;
    z-index: 0;
    margin: auto;
    grid-row: 2/3;
    grid-column: 1/2;
}
 
#slider input:focus + .outer {
    outline: 1px dashed var(--orange);
  }
 
#slider label.inner {
    position: absolute;
    width: 100%;
    height: 100%;
    background: var(--white);
    background: linear-gradient(to left, var(--yellow), var(--orange));
    border-top-left-radius: var(--roundness) !important;
    border-bottom-left-radius: var(--roundness) !important;
    position: absolute;
    transition: all 0.3s cubic-bezier(0.5, 0.4, 0.2, 1);
    text-align: right;
    font-size: calc(var(--roundness) * 2);
    line-height: 1;
  }
  #slider label.inner span {
    position: absolute;
    right: -2px;
    top: calc(50% - var(--roundness) * 2);
    top: calc(var(--roundness) * -.3);
    transition: inherit;
  }

<script class="lazy" data-src="./js/vue.js"></script>
    <script>
        let a = new Vue({
            el:"#slider",
            data() {
                return {
                    val: 70,
                    // 关键点，同时用来动态关联  1：情绪百分比，2：显示出来的文本表情
                }
            },
            mounted() {
                this.val = Math.floor(Math.random() * 101)
            },
            computed: {
        getPlacement: function () {
            return `${(-0.009 * ((this.val * -1) + 104))}em`;
            // 获取位置，因为是计算属性，相当于是与val绑定了，给最下方的span绑定后就等于与上方与val绑定的width，进行“绑定”
        },
        greaterThanFifty: function () {
            return this.val > 50 ? `var(--roundness)` : `0`;
            // val值大于五十之后，边框的变化，可以省略或者不绑定，不关键
        },
        getHappinessColor: function () {
            return `rgba(255, ${106 + (103 / 100 * this.val)}, ${(Math.floor(this.val * -1 / 7.692)) + 13}`;
            // 获取颜色的函数，可以随意更改数值，不过上方颜色过渡更加自然
        },
        getHappiness: function () {
            let mood;
            // 将val值与所有表情“物理绑定”
            if (this.val == 0) {
                mood = "?"
            } else if (this.val < 10) {
                mood = "?"
            } else if (this.val < 20) {
                mood = "?"
            } else if (this.val < 30) {
                mood = "?"
            } else if (this.val < 40) {
                mood = "☹️"
            } else if (this.val < 50) {
                mood = "?"
            } else if (this.val < 60) {
                mood = "?"
            } else if (this.val < 70) {
                mood = "?"
            } else if (this.val < 80) {
                mood = "?"
            } else if (this.val < 90) {
                mood = "?"
            } else if (this.val < 100) {
                mood = "?"
            } else if (this.val == 100) {
                mood = "?"
            }
            return mood;
        }
    }
        })
    </script>