js addition, subtraction, multiplication and division precise calculation method example code

function add(arg1, arg2) {

	 arg1 = arg1.toString(), arg2 = arg2.toString(); // Convert the incoming data into a string var arg1Arr = arg1.split("."), // Split the decimal data from the decimal point arg2Arr = arg2.split("."),
   d1 = arg1Arr.length == 2 ? arg1Arr[1] : "", // Get the length of the decimal point of the first number d2 = arg2Arr.length == 2 ? arg2Arr[1] : ""; // Get the length of the decimal point of the second number var maxLen = Math.max(d1.length, d2.length); // Get the larger value of the decimal point length var m = Math.pow(10, maxLen); // This represents the power of the decimal point length of 10. That is, if the decimal point length is 2, the value of m is 100. If the decimal point length is 3, the value of m is 1000. If you don't understand, please look up the api yourself
  var result = Number(((arg1 * m + arg2 * m) / m).toFixed(maxLen)); // Convert the decimals to integers and add them together, then remove the multiples of the two numbers multiplied and remove the decimal point.var d = arguments[2]; // The user can decide whether to pass the third parameter to define the length of decimals to be retained.return typeof d === "number" ? Number((result).toFixed(d)) : result;
}

add(12.123, 12)

function sun(arg1, arg2) {
return add(arg1, -arg2)
}

function mul(arg1, arg2) {
var r1 = arg1.toString(), // Convert the incoming data into a string r2 = arg2.toString(),
m, resultVal, d = arguments[2];
m = (r1.split(".")[1] ? r1.split(".")[1].length : 0) + (r2.split(".")[1] ? r2.split(".")[1].length : 0); // Get the sum of the decimal places of two numbers // The product algorithm is to remove the decimal point, do integer multiplication and then remove all the powers of 10 resultVal = Number(r1.replace(".", "")) * Number(r2.replace(".", "")) / Math.pow(10, m);

return typeof d !== "number" ? Number(resultVal) : Number(resultVal.toFixed(parseInt(d)));
}

function div(arg1, arg2) {
     var r1 = arg1.toString(),
      r2 = arg2.toString(),
      m, resultVal, d = arguments[2];
     m = (r2.split(".")[1] ? r2.split(".")[1].length : 0) - (r1.split(".")[1] ? r1.split(".")[1].length : 0);
     resultVal = Number(r1.replace(".", "")) / Number(r2.replace(".", "")) * Math.pow(10, m);
     return typeof d !== "number" ? Number(resultVal) : Number(resultVal.toFixed(parseInt(d)));
    }