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JavaScript: Find the shortest possible string which can create a string to make it a palindrome by adding characters to the end of it

JavaScript Basic: Exercise-97 with Solution

Write a JavaScript program to find the shortest possible string which can create a string to make it a palindrome by adding characters to the end of it.

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title> Find the shortest possible string which can create a string to make it a palindrome by adding characters to the end of it</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function build_Palindrome(new_str) {
  var flag;
  for (var i = new_str.length;; i++) {
    flag = true;
    for (var j = 0; j < i - j - 1; j++) {
      if (i - j - 1 < new_str.length && new_str[j] != new_str[i - j - 1]) {
        flag = false;
        break;
      }
    }
    if (flag) {
      for (var j = new_str.length; j < i; j++) {
        new_str += new_str[i - j - 1];
      }
      return new_str;
    }
  }
}

console.log(build_Palindrome("abcddc"))
console.log(build_Palindrome("122"))

Sample Output:

abcddcba
1221

Flowchart:

Flowchart: JavaScript - Find the shortest possible string which can create a string to make it a palindrome by adding characters to the end of it

ES6 Version:

function build_Palindrome(new_str) {
  let flag;
  for (let i = new_str.length;; i++) {
    flag = true;
    for (var j = 0; j < i - j - 1; j++) {
      if (i - j - 1 < new_str.length && new_str[j] != new_str[i - j - 1]) {
        flag = false;
        break;
      }
    }
    if (flag) {
      for (var j = new_str.length; j < i; j++) {
        new_str += new_str[i - j - 1];
      }
      return new_str;
    }
  }
}

console.log(build_Palindrome("abcddc"))
console.log(build_Palindrome("122"))

Live Demo:

See the Pen javascript-basic-exercise-97 by w3resource (@w3resource) on CodePen.


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Previous: Write a JavaScript program to compute the sum of absolute differences of consecutive numbers of a given array of integers.
Next: Write a JavaScript program to switch case of the minimum possible number of letters to make a given string written in the upper case or in the lower case.

What is the difficulty level of this exercise?



JavaScript: Tips of the Day

Promise object

const myPromise = () => Promise.resolve('I have resolved!');

function firstFunction() {
  myPromise().then(res => console.log(res));
  console.log('second');
}

async function secondFunction() {
  console.log(await myPromise());
  console.log('second');
}

firstFunction();
secondFunction();

With a promise, we basically say I want to execute this function, but I'll put it aside for now while it's running since this might take a while. Only when a certain value is resolved (or rejected), and when the call stack is empty, I want to use this value.
We can get this value with both .then and the await keyword in an async function. Although we can get a promise's value with both .then and await, they work a bit differently.
In the firstFunction, we (sort of) put the myPromise function aside while it was running, but continued running the other code, which is console.log('second') in this case. Then, the function resolved with the string I have resolved, which then got logged after it saw that the callstack was empty.
With the await keyword in secondFunction, we literally pause the execution of an async function until the value has been resolved before moving to the next line.
This means that it waited for the myPromise to resolve with the value I have resolved, and only once that happened, we moved to the next line: second got logged.

Ref: https://bit.ly/3jFRBje