函数返回Undefined

Question

我需要一个小代码的小帮助.该函数返回undefined,我想返回总和的console.log.代码在这里http://jsbin.com/jedigigigo/edit?js,console

var addDigits = function a(num) {
  var length = num.toString().length;
  var value = num.toString();
  var sum = 0;
  for (var i = 0; i < value.length; i++) {
    sum += Number(value[i]);
  }
  if (sum > 9) {
    a(sum);
  } else {
    console.log(sum);
    return sum;
  }
};


console.log(addDigits(38));

Answer 1

在if语句中添加return: -

/**
* @param {number} num
* @return {number}
*/

var addDigits = function a(num) {
  var length = num.toString().length;
  var value = num.toString();
  var sum = 0;
  for (var i = 0; i < value.length; i++) {
    sum += Number(value[i]);
  }
  if (sum > 9) {
    return a(sum);
  } else {
    console.log(sum);
    return sum;
  }
};


console.log(addDigits(38));