js两数相除除不尽，直接返回Infinity

前端计算百分比，现在是要748除以805，现在算出来直接是Infinity，要怎么才能正常取值？

const arr1 = ((cumulativeElectric / 10) / (monthElectric / 10)).toFixed(2) * 100 + "";
console.log(Math.round(arr1 * 100) / 100);

var num = (num1/num2)*100+'%';
return Math.round(num * 100)/100;