Question

var subsequences = function(s) {
  if (s==="") {
    return s
  } else {
    var firstLetter = s.charAt(0)
    var restOfWord = s.substring(1)

我正在尝试实现功能

Answer 1

您正在使用for..in循环，该循环用于迭代对象，而不是数组。而是在.split()方法调用返回的数组上使用Array.forEach()方法。

您还应该养成用分号和not rely on automatic semi-colon insertion结束语句的习惯。

var subsequences = function(s) {
  if (s==="") {
    return s;
  } else {
    var firstLetter = s.charAt(0);
    var restOfWord = s.substring(1);

    var subsequencesOfRest = subsequences(restOfWord);

    var result = "";
    subsequencesOfRest.split(",").forEach(function(item){
      result += "," + item;
      result += "," + firstLetter + item;
    });
    result = result.substring(1);
    return result;
  }
};

console.log(subsequences("gc"))

Answer 2

您应该使用in来迭代数组，而不是使用of。

您需要更改的只是一个字：

var subsequences = function(s) {
  if (s==="") {
    return s
  } else {
    var firstLetter = s.charAt(0)
    var restOfWord = s.substring(1)

    var subsequencesOfRest = subsequences(restOfWord)

    var result = ""
    for (var subsequence of subsequencesOfRest.split(",")) {
      result += "," + subsequence
      result += "," + firstLetter + subsequence
    }
    result = result.substring(1)
    return result
  }
}
console.log(subsequences("gc"))

Answer 3

使用for of而不是for in

var subsequences = function(s) {
  if (s==="") {
    return s
  } else {
    var firstLetter = s.charAt(0)
    var restOfWord = s.substring(1)

    var subsequencesOfRest = subsequences(restOfWord)

    var result = ""
    for (let subsequence of subsequencesOfRest.split(",")) {
      result += "," + subsequence
      result += "," + firstLetter + subsequence
     }
    result = result.substring(1)
    return result
  }
}

console.log(subsequences("gc"))

Answer 4

重点是for (var subsequence in subsequencesOfRest.split(",")) { } 当subsequencesOfRest为”时，运行subsequencesOfRest.split（“，”），结果为[“”]，并且子序列是数组中的索引，因此子序列为0。

我为什么要实施？

4 个答案: