チェックディジット計算をjavascriptでやる

let newJancode;
let reCheck;
let num1 = 0;
let num2 = 0;
let checkedNum = 0;
let sum;
let strSum;
let enableNum;

reCheck = result.text.slice(1, result.text.length-1);
for(var i = 0; i < reCheck.length; i++){
  if(i % 2 === 1){
    num1 += Number(reCheck[i]);
  }
}
checkedNum = num1 * 3;
for(var i = 0; i < reCheck.length; i++){
  if(i % 2 === 0){
    num2 += Number(reCheck[i]);
  }
}
sum = checkedNum + num2;
strSum = String(sum);
enableNum = 10 - Number(strSum.slice(strSum.length-1, strSum.length));
newJancode = reCheck + enableNum;