只用svg path命令绘制空心正五边形，需要注意fill的规则

pentagon5.js

//min: 内径长度
//max: 外径长度
function pentagon5(min, max) {
    const minPoint = transform(getBasePoint(min), max);
    const maxPoint = transform(getBasePoint(max), max);
    maxPoint.reverse();

    return toStr(minPoint) + toStr(maxPoint)

    function getBasePoint(base) {
        const sin = Math.sin;
        const cos = Math.cos;
        const pi = Math.PI;
        return [
            [0, -base],
            [base * cos(1/10 * pi), -base * sin(1/10 * pi)],
            [base * sin(1/5 * pi), base * cos(1/5 * pi)],
            [-base * sin(1/5 * pi), base * cos(1/5 * pi)],
            [-base * cos(1/10 * pi), -base * sin(1/10 * pi)]
        ]
    }

    function transform(point, offset) {
        return point.map(arr => arr.map(x => x + offset))
    }

    function toStr(point) {
        let str = '';
        return point.reduce((acc, cur, index)=>{
            const tmp = (~~cur[0]===cur[0] ? ''+cur[0] : cur[0].toFixed(3)) + ',' + (~~cur[1]===cur[1] ? ''+cur[1] : cur[1].toFixed(3));
            if(index===0) {
                acc+='M'+tmp;
            } else {
                acc+='L'+tmp;
            }
            if(index===point.length-1) {
                acc+='Z'
            }
            return acc;
        }, '');
    }
}