使用JavaScript Array find方法报错：期望undefined等于'2015'

核心问题 #

你的函数设计和测试用例的预期不匹配，同时对Array.find()的回调逻辑理解存在偏差：

• 测试用例期望superbowlWin是一个接收赛事记录数组作为参数、直接返回获胜年份的函数；
• 但你写的superbowlWin是给find用的回调函数（接收单个数组元素为参数），导致测试调用时无法正确获取结果，返回undefined。

修正后的代码 #

调整superbowlWin函数，让它直接接收数组参数，内部用find完成匹配逻辑：

const record = [
{ year: "2018", result: "N/A"},
{ year: "2017", result: "N/A"},
{ year: "2016", result: "N/A"},
{ year: "2015", result: "W"},
{ year: "2014", result: "N/A"},
{ year: "2013", result: "L"},
{ year: "2012", result: "N/A"},
{ year: "2011", result: "N/A"},
{ year: "2010", result: "N/A"},
{ year: "2009", result: "N/A"},
{ year: "2008", result: "N/A"},
{ year: "2007", result: "N/A"},
{ year: "2006", result: "N/A"},
{ year: "2005", result: "N/A"},
{ year: "2004", result: "N/A"},
{ year: "2003", result: "N/A"},
{ year: "2002", result: "N/A"},
{ year: "2001", result: "N/A"},
{ year: "2000", result: "N/A"},
{ year: "1999", result: "N/A"},
{ year: "1998", result: "W"},
{ year: "1997", result: "W"},
{ year: "1996", result: "N/A"},
{ year: "1995", result: "N/A"},
{ year: "1994", result: "N/A"},
{ year: "1993", result: "N/A"},
{ year: "1992", result: "N/A"},
{ year: "1991", result: "N/A"},
{ year: "1990", result: "N/A"},
{ year: "1989", result: "L"},
{ year: "1988", result: "N/A"},
{ year: "1987", result: "L"},
{ year: "1986", result: "L"},
{ year: "1985", result: "N/A"},
{ year: "1984", result: "N/A"},
{ year: "1983", result: "N/A"},
{ year: "1982", result: "N/A"},
{ year: "1981", result: "N/A"},
{ year: "1980", result: "N/A"},
{ year: "1979", result: "N/A"},
{ year: "1978", result: "N/A"},
{ year: "1977", result: "N/A"},
{ year: "1976", result: "L"},
{ year: "1975", result: "N/A"},
{ year: "1974", result: "N/A"},
{ year: "1973", result: "N/A"},
{ year: "1972", result: "N/A"},
{ year: "1971", result: "N/A"},
{ year: "1970", result: "N/A"},
{ year: "1969", result: "N/A"},
{ year: "1968", result: "N/A"},
{ year: "1967", result: "N/A"},
{ year: "1966", result: "N/A"},
{ year: "1965", result: "N/A"},
{ year: "1964", result: "N/A"},
{ year: "1963", result: "N/A"},
{ year: "1962", result: "N/A"},
{ year: "1961", result: "N/A"},
{ year: "1960", result: "N/A"}
];

function superbowlWin(record) {
  // 用find找到结果为"W"的记录，回调返回布尔值判断匹配
  const winningEntry = record.find(entry => entry.result === "W");
  // 存在获胜记录则返回年份，否则返回undefined
  return winningEntry ? winningEntry.year : undefined;
}

// 调用示例
console.log(superbowlWin(record)); // 输出 '2015'

原代码的问题解析 #

1. 回调函数逻辑不规范：find的回调函数应该返回布尔值（true/false）来标识当前元素是否符合条件，你返回年份字符串虽然能触发find的匹配（因为非空字符串是真值），但这不是标准写法，容易混淆逻辑。
2. 函数职责不符预期：测试用例应该是直接调用superbowlWin(record)来获取年份，但你的函数只能作为find的回调使用，传入整个数组时，element.result不存在，函数返回undefined，导致断言失败。

内容的提问来源于stack exchange，提问作者McNaughty