Question

How to reverse the middle N characters of a string in Node.js

Answer 1

function reverse_middle_N_characters(s, N) { 
    const len = s.length;
    const mid = (len - N) / 2; 
    let tmp = "";
   
    for (let i = 0; i < mid; i++) 
        tmp += s[i]; 
     
    for (let i = mid + N - 1; i >= mid; i--) 
        tmp += s[i]; 
     
    for (let i = mid + N; i < len; i++) 
         tmp += s[i];
       
    return tmp;
} 
     
      
let s = "abCDEfg"; 
const N = 3; 
       
console.log(reverse_middle_N_characters(s, N));
 
   
    
/*
run:
        
abEDCfg
        
*/
 

 

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Answer 2

function reverse_middle_N_characters(str, N) { 
    if (N <= 0 || N > str.length) {
        return str; 
    }

    const start = Math.floor((str.length - N) / 2);
    const end = start + N;

    const beforeMiddle = str.slice(0, start);
    const middle = str.slice(start, end).split('').reverse().join('');
    const afterMiddle = str.slice(end);

    return beforeMiddle + middle + afterMiddle;
} 
    
     
let s = "abCDEFgh"; 
const N = 4; 
      
console.log(reverse_middle_N_characters(s, N));


   
/*
run:
       
abFEDCgh
       
*/

 

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