使用words.push(str.split(" "))时，数组words看起来像

[
    ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"]
]

另一个问题是，当您在for 中检查longest[0].length 的第一次迭代时，它是undefined.导致错误

Another problem is that when you check longest[0].length for the first iteration in the for, it is undefined. Which results in the error

未捕获的类型错误:无法读取未定义的属性长度"

Uncaught TypeError: Cannot read property 'length' of undefined

要解决这个问题，您可以使用 longest 作为 string 而不是 array.并在 for 中，将 length 大于当前 longest 字符串的字符串分配给它.

To solve this, you can use longest as string instead of array. And in the for, assign the string having the length greater than the current longest string to it.

在函数的最后，可以返回最长的字符串.

At the end of the function, you can return the longest string.

问题/建议:

1. 使用str.split(' ')直接赋值给words变量
2. 使用 longest 作为 string 变量而不是 array 和 initialize 它为空字符串，即 ''，避免上述错误
3. 比较longest的长度和words数组中的字符串
4. 如果words数组中字符串的长度大于longest，则更新longest.
5. 使用s+将字符串拆分空格

1. Use str.split(' ') to directly assignment to words variable
2. Use longest as string variable instead of array and initialize it to empty string, i.e. '', to avoid the above error
3. Compare the length of the longest with the string in the words array
4. If the length of the string in words array is greater than the longest, update the longest.
5. Use s+ to split the string by spaces

function findLongestWord(str) {
  var words = str.split(/s+/);
  var longest = '';

  for (var i = 0; i < words.length; i++) {
    if (words[i].length > longest.length) {
      longest = words[i];
    }
  }
  return longest;
}

var longestWord = findLongestWord('The quick brown fox jumped over the lazy dog');

document.write('Longest Word: "' + longestWord + '"');
document.write('<br />Longest Word Length: ' + longestWord.length);