总结javascript加减乘除精度计算实现（已测试，保证正确）

加减乘除精度计算问题
加法精度

function add(...val) {
			      let max = 0
			      let count = 0
			      for (let i = 0; i < val.length; i++) {
			        const strVal = val[i].toString()
			        const index = strVal.indexOf('.')
			        let num = 0
			        if (index > -1) {
			          num = strVal.length - 1 - index
			          max = num > max ? num : max
			        }
			      }
			      for (let i = 0; i < val.length; i++) {
			        count += Math.round(val[i] * Math.pow(10, max))//Math.round() 函数返回一个数字四舍五入后最接近的整数。
			      }
			      return count / Math.pow(10, max)
			    }
			console.log(add(0.1,0.2))

乘法精度

function accMul(arg1, arg2) {
    var m = 0,
        s1 = arg1.toString(),
        s2 = arg2.toString();
    try {
        m += s1.split(".")[1].length
    } catch (e) {}
    try {
        m += s2.split(".")[1].length
    } catch (e) {}
    return Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m)
}

减法精度

function Subtr(arg1,arg2){
				     var r1,r2,m,n;
				     try{r1=arg1.toString().split(".")[1].length}catch(e){r1=0}
				     try{r2=arg2.toString().split(".")[1].length}catch(e){r2=0}
				     m=Math.pow(10,Math.max(r1,r2));
				     //last modify by deeka
				     //动态控制精度长度
				     n=(r1>=r2)?r1:r2;
				     return ((arg1*m-arg2*m)/m).toFixed(n);
				}
				
				 console.log(Subtr(0.1,0.2))

除法精度

   function exc(val, valTwo = 100) {
      const strVal = val.toString()
      const strValTwo = valTwo.toString()
      const index = strVal.indexOf('.')
      const indexTwo = strValTwo.indexOf('.')
      const num = [0, 0]
      if (index > -1) {
        num[0] = strVal.length - 1 - index
      }
      if (indexTwo > -1) {
        num[1] = strValTwo.length - 1 - index
      }
      return Math.round(val * Math.pow(10, num[0])) / (Math.round((valTwo * Math.pow(10, num[1]))) * Math.pow(10, num[0] - num[1]))
    }