在JavaScript中查找字符串中最长单词的三种方法(推荐)
本文基于FreeCodeCamp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(“Thequickbrownfoxjumpedoverthelazydog”)返回一个数字
- findLongestWord(“Thequickbrownfoxjumpedoverthelazydog”)返回6
- findLongestWord(“Maytheforcebewithyou”)返回5
- findLongestWord(“Googledoabarrelroll”)返回6
- findLongestWord(“Whatistheaverageairspeedvelocityofanunladenswallow”)返回8
- findLongestWord(“Whatifwetryasuper-longwordsuchasotorhinolaryngology”)返回19
functionfindLongestWord(str){
returnstr.length;
}
findLongestWord("Thequickbrownfoxjumpedoverthelazydog");
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
varstrSplit=“Thequickbrownfoxjumpedoverthelazydog”.split(‘‘);
它将输出一个由单词组成的数组：
varstrSplit=[“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：
varstrSplit= [“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”];
functionfindLongestWord(str){
//Step1.Splitthestringintoanarrayofstrings
varstrSplit=str.split('');
//varstrSplit="Thequickbrownfoxjumpedoverthelazydog".split('');
//varstrSplit=["The","quick","brown","fox","jumped","over","the","lazy","dog"];
//Step2.Initiateavariablethatwillholdthelengthofthelongestword
varlongestWord=0;
//Step3.CreatetheFORloop
for(vari=0;ilongestWord){//IfstrSplit[i].lengthisgreaterthantheworditiscomparedwith...
longestWord=strSplit[i].length;//...thenlongestWordtakesthisnewvalue
}
}
/*HerestrSplit.length=9
Foreachiteration:i=?ilongestWord)?longestWord=strSplit[i].length
1stiteration:0yes1if("The".length>0)?=>if(3>0)?longestWord=3
2nditeration:1yes2if("quick".length>3)?=>if(5>3)?longestWord=5
3rditeration:2yes3if("brown".length>5)?=>if(5>5)?longestWord=5
4thiteration:3yes4if("fox".length>5)?=>if(3>5)?longestWord=5
5thiteration:4yes5if("jumped".length>5)?=>if(6>5)?longestWord=6
6thiteration:5yes6if("over".length>6)?=>if(4>6)?longestWord=6
7thiteration:6yes7if("the".length>6)?=>if(3>6)?longestWord=6
8thiteration:7yes8if("lazy".length>6)?=>if(4>6)?longestWord=6
9thiteration:8yes9if("dog".length>6)?=>if(3>6)?longestWord=6
10thiteration:9no
EndoftheFORLoop*/
//Step4.Returnthelongestword
returnlongestWord;//6
}
findLongestWord("Thequickbrownfoxjumpedoverthelazydog");
没有注释：
functionfindLongestWord(str){
varstrSplit=str.split('');
varlongestWord=0;
for(vari=0;ilongestWord){
longestWord=strSplit[i].length;
}
}
returnlongestWord;
}
findLongestWord("Thequickbrownfoxjumpedoverthelazydog");
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
varsortArray=[“The”,“quick”,“brown”,“fox”,“jumped”,“over”,“the”,“lazy”,“dog”].sort();
我们将得到以下输出：
varsortArray=[“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
[].sort(function(firstElement,secondElement){returnsecondElement.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。
functionfindLongestWord(str){
//Step1.Splitthestringintoanarrayofstrings
varstrSplit=str.split('');
//varstrSplit="Thequickbrownfoxjumpedoverthelazydog".split('');
//varstrSplit=["The","quick","brown","fox","jumped","over","the","lazy","dog"];
//Step2.Sorttheelementsinthearray
varlongestWord=strSplit.sort(function(a,b){
returnb.length-a.length;
});
/*Sortingprocess
abb.lengtha.lengthvarlongestWord
"The""quick"53["quick","The"]
"quick""brown"55["quick","brown","The"]
"brown""fox"35["quick","brown","The","fox"]
"fox""jumped"63["jumped",quick","brown","The","fox"]
"jumped""over"46["jumped",quick","brown","over","The","fox"]
"over""the"34["jumped",quick","brown","over","The","fox","the"]
"the""lazy"43["jumped",quick","brown","over","lazy","The","fox","the"]
"lazy""dog"34["jumped",quick","brown","over","lazy","The","fox","the","dog"]
*/
//Step3.Returnthelengthofthefirstelementofthearray
returnlongestWord[0].length;//varlongestWord=["jumped","quick","brown","over","lazy","The","fox","the","dog"];
//longestWord[0]="jumped"=>jumped".length=>6
}
findLongestWord("Thequickbrownfoxjumpedoverthelazydog");
没有注释：
functionfindLongestWord(str){
varlongestWord=str.split('').sort(function(a,b){returnb.length-a.length;});
returnlongestWord[0].length;
}
findLongestWord("Thequickbrownfoxjumpedoverthelazydog");
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“”。
[].reduce(function(previousValue,currentValue){...},“”);
functionfindLongestWord(str){
//Step1.Splitthestringintoanarrayofstrings
varstrSplit=str.split('');
//varstrSplit="Thequickbrownfoxjumpedoverthelazydog".split('');
//varstrSplit=["The","quick","brown","fox","jumped","over","the","lazy","dog"];
//Step2.Usethereducemethod
varlongestWord=strSplit.reduce(function(longest,currentWord){
if(currentWord.length>longest.length)
returncurrentWord;
else
returnlongest;
},"");
/*Reduceprocess
currentWordlongestcurrentWord.lengthlongest.lengthif(currentWord.length>longest.length)?varlongestWord
"The"""30yes"The"
"quick""The"53yes"quick"
"brown""quick"55no"quick"
"fox""quick"35no"quick"
"jumped""quick"65yes"jumped"
"over""jumped"46no"jumped"
"the""jumped"36no"jumped"
"lazy""jumped"46no"jumped"
"dog""jumped"36no"jumped"
*/
//Step3.ReturnthelengthofthelongestWord
returnlongestWord.length;//varlongestWord="jumped"
//longestWord.length=>"jumped".length=>6
}
findLongestWord("Thequickbrownfoxjumpedoverthelazydog");
没有注释：
functionfindLongestWord(str){
varlongestWord=str.split('').reduce(function(longest,currentWord){
returncurrentWord.length>longest.length?currentWord:longest;
},"");
returnlongestWord.length;
}
findLongestWord("Thequickbrownfoxjumpedoverthelazydog");
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