从 javascript 中的递归函数中获取未定义

Question

我花了大约一个小时试图弄清楚为什么我从这个函数中得到未定义，这个函数运行良好，它在条件触发并且 randomAlphabet 的值正确时停止，当然是愚蠢的错误，但它让我觉得很烦人。这是代码：

(function() {

  var getAlphabet = function() {
    var alphabet = [];
    for ( var asciiCode = 97; asciiCode < 123; asciiCode++ ) {
      alphabet.push(String.fromCharCode(asciiCode));
    }
    return alphabet;
  };

  var getRandomAlphabet = function(alphabet, randomAlphabet) {

    var alphabet = alphabet || getAlphabet();
    var alphabetLength = alphabet.length;
    var randomAlphabet = randomAlphabet || [];

    if ( alphabetLength === 0 ) {
      return randomAlphabet;
    };

    var getRandomIndex = function(min, max) {
      return Math.floor(Math.random() * (max - min) + min);
    };

    // remove the random item from the original alphabet
    var randomIndex = getRandomIndex(0, alphabetLength);
    var randomItem = alphabet.splice(randomIndex, 1)[0]; 

    // add the random item to the random alphabet
    randomAlphabet = randomAlphabet.concat(randomItem);

    getRandomAlphabet(alphabet, randomAlphabet);

  };

  // this returns undefined
  console.log(getRandomAlphabet()); 

})();

Answer 1

唯一的问题是您需要 return getRandomAlphabet 方法

(function() {

  var getAlphabet = function() {
    var alphabet = [];
    for ( var asciiCode = 97; asciiCode < 123; asciiCode++ ) {
      alphabet.push(String.fromCharCode(asciiCode));
    }
    return alphabet;
  };

  var getRandomAlphabet = function(alphabet, randomAlphabet) {

    var alphabet = alphabet || getAlphabet();
    var alphabetLength = alphabet.length;
    var randomAlphabet = randomAlphabet || [];

    if ( alphabetLength === 0 ) {
      return randomAlphabet;
    };

    var getRandomIndex = function(min, max) {
      return Math.floor(Math.random() * (max - min) + min);
    };

    // remove the random item from the original alphabet
    var randomIndex = getRandomIndex(0, alphabetLength);
    var randomItem = alphabet.splice(randomIndex, 1)[0]; 

    // add the random item to the random alphabet
    randomAlphabet = randomAlphabet.concat(randomItem);

    return getRandomAlphabet(alphabet, randomAlphabet);

  };

  // this returns undefined
  console.log(getRandomAlphabet()); 

})();

从 javascript 中的递归函数中获取未定义

getting undefined from recursive function in javascript

javascript

recursion