将数字从个位开始三位分隔的方法记录（tx笔试）

  function trans(num) {
        let numTosArray = num.toString().split('').reverse();
        let returnArray = [];
        for (let i = 0; i < numTosArray.length; i++) {
            if (!((i + 1) % 3)) {
                if (i === numTosArray.length - 1) {
                    returnArray.push(numTosArray[i])
                } else {
                    returnArray.push(',' + numTosArray[i])
                }
            } else {
                returnArray.push(numTosArray[i])
            }
        }
        return returnArray.reverse().join('');
    }

    console.log(trans(123452342423));//123,452,342,423