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在JavaScript中查找字符串中最长单词的三种方法(推荐)

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本文基于Free Code Camp基本算法脚本“查找字符串中最长的单词”.

在此算法中,我们要查看每个单词并计算每个单词中有多少个字母。然后,比较计数以确定哪个单词的字符最多,并返回最长单词的长度.

在本文中,我将解释三种方法。首先使用FOR循环,其次使用sort()方法,第三次使用reduce()方法.

算法挑战 。

  • 返回提供的句子中最长单词的长度。
  • 您的回复应该是一个数字。

提供的测试用例 。

  • findLongestWord(“The quick brown fox jumped over the lazy dog”)返回一个数字
  • findLongestWord(“The quick brown fox jumped over the lazy dog”)返回6
  • findLongestWord(“May the force be with you”)返回5
  • findLongestWord(“Google do a barrel roll”)返回6
  • findLongestWord(“What is the average airspeed velocity of an unladen swallow”)返回8
  • findLongestWord(“What if we try a super-long word such as otorhinolaryngology”)返回19
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function findLongestWord(str) {
  return str.length;
}
findLongestWord( "The quick brown fox jumped over the lazy dog" );

1.使用FOR循环查找最长的单词 。

对于此解决方案,我们将使用String.prototype.split()方法 。

  • split()的方法通过分离串分成子串分割字符串对象到字符串数组。

我们将需要在split()方法的括号之间添加一个空格 。

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var strSplit = “The quick brown fox jumped over the lazy dog”.split(‘ ‘);

它将输出一个由单词组成的数组:

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var strSplit = [“The”, “quick”, “brown”, “fox”, “jumped”, “over”, “the”, “lazy”, “dog”];

如果不在括号中添加空格,则将得到以下输出:

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var strSplit =
[“T”, “h”, “e”, “ “, “q”, “u”, “i”, “c”, “k”, “ “, “b”, “r”, “o”, “w”, “n”, “ “, “f”, “o”, “x”, “ “, “j”, “u”, “m”, “p”, “e”, “d”, “ “, “o”, “v”, “e”, “r”, “ “, “t”, “h”, “e”, “ “, “l”, “a”, “z”, “y”, “ “, “d”, “o”, “g”];
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function findLongestWord(str) {
  // Step 1. Split the string into an array of strings
  var strSplit = str.split( ' ' );
  // var strSplit = "The quick brown fox jumped over the lazy dog".split(' ');
  // var strSplit = ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"];
 
  // Step 2. Initiate a variable that will hold the length of the longest word
  var longestWord = 0;
 
  // Step 3. Create the FOR loop
  for ( var i = 0; i < strSplit.length; i++){
  if (strSplit[i].length > longestWord){ // If strSplit[i].length is greater than the word it is compared with...
  longestWord = strSplit[i].length; // ...then longestWord takes this new value
   }
  }
  /* Here strSplit.length = 9
   For each iteration: i = ? i < strSplit.length? i++ if(strSplit[i].length > longestWord)? longestWord = strSplit[i].length
   1st iteration:  0    yes    1 if("The".length > 0)? => if(3 > 0)?  longestWord = 3
   2nd iteration:  1    yes    2 if("quick".length > 3)? => if(5 > 3)? longestWord = 5
   3rd iteration:  2    yes    3 if("brown".length > 5)? => if(5 > 5)? longestWord = 5
   4th iteration:  3    yes    4 if("fox".length > 5)? => if(3 > 5)?  longestWord = 5
   5th iteration:  4    yes    5 if("jumped".length > 5)? => if(6 > 5)? longestWord = 6
   6th iteration:  5    yes    6 if("over".length > 6)? => if(4 > 6)? longestWord = 6
   7th iteration:  6    yes    7 if("the".length > 6)? => if(3 > 6)?  longestWord = 6
   8th iteration:  7    yes    8 if("lazy".length > 6)? => if(4 > 6)? longestWord = 6
   9th iteration:  8    yes    9 if("dog".length > 6)? => if(3 > 6)?  longestWord = 6
   10th iteration:  9    no   
   End of the FOR Loop*/
 
  //Step 4. Return the longest word
  return longestWord; // 6
}
 
findLongestWord( "The quick brown fox jumped over the lazy dog" );

没有注释:

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function findLongestWord(str) {
  var strSplit = str.split( ' ' );
  var longestWord = 0;
  for ( var i = 0; i < strSplit.length; i++){
  if (strSplit[i].length > longestWord){
  longestWord = strSplit[i].length;
   }
  }
  return longestWord;
}
findLongestWord( "The quick brown fox jumped over the lazy dog" );

2.使用sort()方法找到最长的单词 。

对于此解决方案,我们将使用Array.prototype.sort()方法按照某种排序标准对数组进行排序,然后返回此数组的第一个元素的长度.

  • sort()的方法进行排序的阵列的代替元素并返回数组。

就我们而言,如果我们只是对数组排序 。

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var sortArray = [“The”, “quick”, “brown”, “fox”, “jumped”, “over”, “the”, “lazy”, “dog”].sort();

我们将得到以下输出:

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var sortArray = [“The”, “brown”, “dog”, “fox”, “jumped”, “lazy”, “over”, “quick”, “the”];

在Unicode中,数字在大写字母之前,而在小写字母之前.

我们需要按照某种排序标准对元素进行排序 。

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[].sort( function (firstElement, secondElement) {  return secondElement.length — firstElement.length; })

比较第二个元素的长度和数组中第一个元素的长度.

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function findLongestWord(str) {
  // Step 1. Split the string into an array of strings
  var strSplit = str.split( ' ' );
  // var strSplit = "The quick brown fox jumped over the lazy dog".split(' ');
  // var strSplit = ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"];
 
  // Step 2. Sort the elements in the array
  var longestWord = strSplit.sort( function (a, b) {
  return b.length - a.length;
  });
  /* Sorting process
  a   b   b.length  a.length  var longestWord
  "The"  "quick"   5   3   ["quick", "The"]
  "quick" "brown"   5   5   ["quick", "brown", "The"]
  "brown" "fox"    3   5   ["quick", "brown", "The", "fox"]
  "fox"  "jumped"   6   3   ["jumped", quick", "brown", "The", "fox"]
  "jumped" "over"    4   6   ["jumped", quick", "brown", "over", "The", "fox"]
  "over"  "the"    3   4   ["jumped", quick", "brown", "over", "The", "fox", "the"]
  "the"  "lazy"    4   3   ["jumped", quick", "brown", "over", "lazy", "The", "fox", "the"]
  "lazy"  "dog"    3   4   ["jumped", quick", "brown", "over", "lazy", "The", "fox", "the", "dog"]
  */
 
  // Step 3. Return the length of the first element of the array
  return longestWord[0].length; // var longestWord = ["jumped", "quick", "brown", "over", "lazy", "The", "fox", "the", "dog"];
         // longestWord[0]="jumped" => jumped".length => 6
}
 
findLongestWord( "The quick brown fox jumped over the lazy dog" );

没有注释:

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function findLongestWord(str) {
  var longestWord = str.split( ' ' ).sort( function (a, b) { return b.length - a.length; });
  return longestWord[0].length;
}
findLongestWord( "The quick brown fox jumped over the lazy dog" );

3.使用reduce()方法找到最长的单词 。

对于此解决方案,我们将使用Array.prototype.reduce().

  • reduce()的方法应用于对一个储液器的功能和所述阵列的每一值(从左到右),以将其降低到一个值。

reduce()对数组中存在的每个元素执行一次回调函数.

您可以提供一个初始值作为要减少的第二个参数,这里我们将添加一个空字符串“”.

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[].reduce( function (previousValue, currentValue) {...}, “”);
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function findLongestWord(str) {
  // Step 1. Split the string into an array of strings
  var strSplit = str.split( ' ' );
  // var strSplit = "The quick brown fox jumped over the lazy dog".split(' ');
  // var strSplit = ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"];
 
  // Step 2. Use the reduce method
  var longestWord = strSplit.reduce( function (longest, currentWord) {
  if (currentWord.length > longest.length)
   return currentWord;
  else
   return longest;
  }, "" );
 
  /* Reduce process
  currentWord  longest  currentWord.length  longest.length if(currentWord.length > longest.length)? var longestWord
  "The"    ""     3      0        yes       "The"
  "quick"   "The"    5      3        yes       "quick"
  "brown"   "quick"    5      5        no       "quick"
  "fox"    "quick"    3      5        no       "quick"
  "jumped"   "quick"    6      5        yes       "jumped"
  "over"   "jumped"   4      6        no       "jumped"
  "the"    "jumped"   3      6        no       "jumped"
  "lazy"   "jumped"   4      6        no       "jumped"
  "dog"    "jumped"   3      6        no       "jumped"
  */
 
  // Step 3. Return the length of the longestWord
  return longestWord.length; // var longestWord = "jumped"
         // longestWord.length => "jumped".length => 6
}
 
findLongestWord( "The quick brown fox jumped over the lazy dog" );

没有注释:

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function findLongestWord(str) {
  var longestWord = str.split( ' ' ).reduce( function (longest, currentWord) {
  return currentWord.length > longest.length ? currentWord : longest;
  }, "" );
  return longestWord.length;
}
findLongestWord( "The quick brown fox jumped over the lazy dog" );

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原文链接:https://blog.csdn.net/qq_25879801/article/details/111408976 。

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