实现效果图：

svg相关知识

这里只介绍本次用到的元素，更多详情：SVG：可缩放矢量图形

• defs：定义需要重复利用的图形元素
• linearGradient：定义线性渐变，用来图形元素的填充或描边使用
• stop：元素或者元素的子元素，用来描述渐变色的坡度
• circle：基于圆心和半径创建圆形
• cx：定义中心点的x坐标
• cy：定义中心点的y坐标
• r：定义圆的半径
• fill：（对于形状元素）用来定义内部颜色
• stroke：图形外轮廓颜色
• stroke-width：外轮廓宽度
• stroke-dasharray：描边的点划线的图案范式（线段，直线。。。）
• stroke-linecap：开放自路径两端的形状（平角，圆角）
• transform：用来设置动画（非svg属性）

实现代码

1. 定义一个可复用的渐变色

<defs>
    <linearGradient id="color">
        <stop offset="0%"  stop-color="#229453"/>
        <stop offset="50%"  stop-color="#66c18c"/>
        <stop offset="100%" stop-color="#b9dec9"/>
    </linearGradient>
</defs>

2. 增加一个外圈的圆，用来包住进度条（旋转整个圆，使缺口朝下）

<circle cx='160' cy='160' r='140' stroke='#999999' stroke-width="20" fill="none" stroke-dasharray="659,300" stroke-linecap="round" transform="rotate(135, 160, 160)"></circle>

3. 增加一个内部的圆，当进度条背景

<circle cx='160' cy='160' r='140' stroke='#ffffff' stroke-width="10" fill="none"  stroke-dasharray="659,300" stroke-linecap="round" transform="rotate(135, 160, 160)"></circle>

4. 增加进度条的圆（动画是为了有进度条移动的效果）

<circle id="circle" cx='160' cy='160' r='140' stroke='url(#color)' stroke-width="10" fill="none" style="stroke-dasharray: 0,900; transition: stroke-dasharray 2s" stroke-linecap="round" transform="rotate(135, 160, 160)"></circle>

5. 写一点js代码来改变进度条长度

const circle = document.getElementById('circle')
setTimeout(()=> {
  circle.style.strokeDasharray = '600,500'
}, 2000)

完整代码

<div>
      <svg style="background: #ffffff" width="320" height="320"  viewBox="0 0 320 320">
        <defs>
            <linearGradient id="color">
                <stop offset="0%"  stop-color="#229453"/>
                <stop offset="50%"  stop-color="#66c18c"/>
                <stop offset="100%" stop-color="#b9dec9"/>
            </linearGradient>
        </defs>
        <circle cx='160' cy='160' r='140' stroke='#999999' stroke-width="20" fill="none" stroke-dasharray="659,300" stroke-linecap="round" transform="rotate(135, 160, 160)"></circle>
        <circle cx='160' cy='160' r='140' stroke='#ffffff' stroke-width="10" fill="none"  stroke-dasharray="659,300" stroke-linecap="round" transform="rotate(135, 160, 160)"></circle>
        <circle id="circle" cx='160' cy='160' r='140' stroke='url(#color)' stroke-width="10" fill="none" style="stroke-dasharray: 0,900; transition: stroke-dasharray 2s" stroke-linecap="round" transform="rotate(135, 160, 160)"></circle>
      </svg>
    </div>

const circle = document.getElementById('circle')
setTimeout(()=> {
 circle.style.strokeDasharray = '600,500'
}, 2000)