Summary of the FCC's JS basic algorithm 1

1. Flipping a string

Solution: First convert the string into an array, then use the reverse method of the array to flip the order of the arrays, and finally convert the array into strings.

1 function reversestring (str) {2   var arr = [];    3   arr = Str.split (""); 4   arr.reverse (); 5   str = Arr.join (""); 6   return str; 7 }89 reversestring ("Hello");

It is mainly used for string.split (), Array.reverse (), Array.join ().

2. Calculate the factorial of an integer

Solution: F (n) =n*f (n-1)

1 functionfactorialize (num) {2   if(Num <= 1) {3     return1;4}Else {5num = num * Factorialize (num-1);6   }7   returnnum;8 }9 TenFactorialize (5);

This is a recursive function, in the study of "JS Advanced Programming" recursive function discovery, such as the code will be shallow copy and put factorialize=null error, so apply Arguments.callee point to the executing pointer

1 function factorialize (num) {2   if (Num <= 1) {3     return 1; 4   Else {5     num = num * Arguments.callee (num-1); 6   }7   return  num; 8 }

However, in strict mode, you cannot access Arguments.callee. Again improved as follows

1 var factorialize = (function  f (num) {2   if(num <= 1) {  3     return 1; 4   Else {5     num = num * F (num-1); 6   }7   return  num; 8 }

3. Check if the string is Palindrome

Workaround: First ignore the string punctuation, capitalization, and space, then decompose the string into an array and then invert it into a new string, comparing the two strings before and after

1 functionpalindrome (str) {2   //Good luck!3str = str.replace (/\w+/g, "");4str = str.replace (/\_+/g, "");5str =str.tolowercase ();6   vararr = Str.split ("");7arr =arr.reverse ();8   varSTR2 = Arr.join ("");9   if(str = =str2) {Ten     return true; One}Else { A     return false; -   } - } thePalindrome ("Almostomla");

4. Find the longest word in the provided sentence and calculate its length.

Workaround: Iterate to compare word lengths

1 functionFindlongestword (str) {2   vararr = Str.split ("");3   varARR2 = [];4   varA = 0;5    for(vari = 0; i < arr.length; i++) {6     varb =arr[i].length;7     if(B >a) {8A =b;9     }Ten } One   returnA; A } -Findlongestword ("What if we try a super-long word such as otorhinolaryngology");

5. The first letter of each word in the string is capitalized, the remainder is lowercase

Solution: All words are first converted to lowercase, and then the first letter of each word is iterated instead

1 functiontitlecase (str) {2str =str.tolowercase ();3   vararr = Str.split ("");4   varSTR2 = "";5   varARR2 = [];6    for(vari = 0; i < arr.length; i++) {7     varA = Arr[i][0].touppercase ();8     varSTR1 = Arr[i].replace (/^\w/, a);9 Arr2.push (str1);Ten   } OneSTR2 = Arr2.join (""); A   returnstr2; - } -  theTitlecase ("I ' m a Little tea pot");

6. The large array contains 4 decimal groups, each of which finds the maximum value in each decimal group, and then concatenates them to form a new array

Workaround: The first method, iterate to find the maximum value

function Largestoffour (arr) {
var arr1 = [];    for (var i = 0; i < arr.length; i++) {    var a = 0;      for (var j = 0; J < Arr[i].length; J + +) {      if(Arr[i][j] > a        ) {=
   
     arr[i][j];      }    }    Arr1.push (a);  }   
    return 
    arr1;}
   

The second method, the direct use of Math.max ()

1 functionLargestoffour (arr) {2 varARR2 = [];3    for(vari = 0; i < arr.length; i++) {4     varARR1 =Arr[i];5     varA = Math.max.apply (NULL, arr1);6 Arr2.push (a);7   }8   returnarr2;9}

7. Check whether a string ends with the specified string

1 functionconfirmending (str, target) {2   varA =target.length;3   varb = Str.substr (-a);4   if(b = =target) {5     return true;6}Else {7     return false;8   }9 }Ten  OneConfirmending ("Bastian", "n");

8. Repeat a specified string of n times

1 functionrepeat (str, num) {2   vararr = [];3    for(vari= 0; i < num; i++) {4Arr[i] =str;5   }6str = Arr.join ("");7   returnstr;8 }9 TenRepeat ("ABC", 3);

Summary of the FCC's JS basic algorithm 1