js处理科学计数法

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function toolNumber(num_str) {
         num_str = num_str.toString();
         if (num_str.indexOf("+") != -1) {
           num_str = num_str.replace("+", "");
         }
         if (num_str.indexOf("E") != -1 || num_str.indexOf("e") != -1) {
               var resValue = "",
            power = "",
            result = null,
            dotIndex = 0,
            resArr = [],
            sym = "";
               var numStr = num_str.toString();
               if (numStr[0] == "-") {
                //如果为负数，转成正数处理，先去掉‘-’号，并保存‘-’.
                 numStr = numStr.substr(1);
                 sym = "-";
               }
               if (numStr.indexOf("E") != -1 || numStr.indexOf("e") != -1) {
                 var regExp = new RegExp(
                   "^(((\\d+.?\\d+)|(\\d+))[Ee]{1}((-(\\d+))|(\\d+)))$",
                   "ig"
            );
            result = regExp.exec(numStr);
            if (result != null) {
                resValue = result[2];
                   power = result[5];
                   result = null;
            }
            if (!resValue && !power) {
                return false;
            }
            dotIndex = resValue.indexOf(".") == -1 ? 0 : resValue.indexOf(".");
            resValue = resValue.replace(".", "");
            resArr = resValue.split("");
            if (Number(power) >= 0) {
                var subres = resValue.substr(dotIndex);
                   power = Number(power);
                   //幂数大于小数点后面的数字位数时，后面加0
                   for (var i = 0; i <= power - subres.length; i++) {
                     resArr.push("0");
                   }
                   if (power - subres.length < 0) {
                     resArr.splice(dotIndex + power, 0, ".");
                   }
             } else {
                 power = power.replace("-", "");
                   power = Number(power);
                   //幂数大于等于 小数点的index位置, 前面加0
                   for (var i = 0; i < power - dotIndex; i++) {
                     resArr.unshift("0");
                   }
                var n = power - dotIndex >= 0 ? 1 : -(power - dotIndex);
                resArr.splice(n, 0, ".");
            }
        }
            resValue = resArr.join("");
               return sym + resValue;
        } else {
               return num_str;
        }
    }

 

来源：https://www.cnblogs.com/hnzkljq/p/11525883.html