将函数作为参数传入时，我的JavaScript函数为何返回undefined？

问题根源 #

1. getRelevantSentences逻辑错误：
   • 未遍历sentences数组，反而把整个数组传给了about函数（about仅接受单个字符串）
   • 仅当传入的整个数组满足条件时才返回结果，否则函数无返回值，直接输出undefined
2. isRelevant逻辑错误：
   • 循环中只要第一个topic不匹配就直接返回false，不会检查后续的topic词，导致漏判
3. 输入数据格式错误：
   • sentences定义缺少数组括号，合法写法应包裹在[]内

修正后的完整代码 #

1. 修复isRelevant函数 #

/**
 * @param {string[]} topics - an array of topic words
 * @param {string} sentence - a space-separated string of words
 * @returns {boolean} whether `sentence` contains any of the words in `topics`
 */
const isRelevant = (topics, sentence) => {
  for(let i=0; i<topics.length;i++){
    if (sentence.includes(topics[i])) {
      return true;
    }
  }
  return false; // 遍历完所有topic都不匹配时才返回false
};

2. 修复getRelevantSentences函数 #

/**
 * @param {(sentence: string) => boolean} criterion - a function that
 *  takes a sentence and returns a boolean
 * @param {string[]} sentences - an array of space-separated strings of words
 * @returns {string[]} the subset of `sentences` for which `criterion` returns true
 */
const getRelevantSentences = (criterion, sentences) => {
    const arr = [];
    // 遍历数组内的每一个句子
    for(const sentence of sentences) {
        if(criterion(sentence)) {
            arr.push(sentence);
        }
    }
    return arr; // 无论是否匹配到，都返回数组（空数组或匹配结果）
};

// 更简洁的写法可直接用数组filter方法：
// const getRelevantSentences = (criterion, sentences) => sentences.filter(criterion);

3. 正确的输入与调用示例 #

// 创建指定主题的判断函数
const dogTopics = ["dog"];
const aboutDogs = about(dogTopics);

// 正确定义句子数组
const sentences = ["I have a pet dog", "I have a pet cat", "I don't have any pets"];

// 调用函数并输出结果
const result = getRelevantSentences(aboutDogs, sentences);
console.log(result); // 输出: ["I have a pet dog"]

内容的提问来源于stack exchange，提问作者antjuh