These are chat archives for camperbot/bonfire-check-for-palindromes

13th
Nov 2015
Yosafat Ariel
@yoskakomba
Nov 13 2015 00:31
hint
CamperBot
@camperbot
Nov 13 2015 00:31

hint [1/9]

## :construction: After this are possible spoiler hints.

Make sure you've tried to hard to solve it yourself before proceeding. :construction:

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:40
hint
CamperBot
@camperbot
Nov 13 2015 00:40

hint [2/9]

Explanation:

You have to check if the string you get as an input is a palindrome and return true if it is, and false otherwise.

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:40
hint
CamperBot
@camperbot
Nov 13 2015 00:40

hint [3/9]

Hint: 1

You may use regular expressions (RegExp) to remove unwanted characters from the string.

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:40
hint
CamperBot
@camperbot
Nov 13 2015 00:40

hint [4/9]

Hint: 2

You may use Array.prototype.split and Array.prototype.join methods or for loop.

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:40
hint
CamperBot
@camperbot
Nov 13 2015 00:40

hint [5/9]

Hint: 3

You may lowercase the string using String.prototype.toLowerCase.

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:40
hint
CamperBot
@camperbot
Nov 13 2015 00:40

hint [6/9]

Spoiler Alert!

687474703a2f2f7777772e796f75726472756d2e636f6d2f796f75726472756d2f696d616765732f323030372f31302f31302f7265645f7761726e696e675f7369676e5f322e676966.gif

Solution ahead!

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:40
hint
CamperBot
@camperbot
Nov 13 2015 00:40

hint [7/9]

First

function palindrome(str) {
  var normalizedStr = str.replace(/[\W_]/g, '').toLowerCase();
  var reverseStr = normalizedStr.split('').reverse().join('');
  return normalizedStr === reverseStr;
}

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:40
hint
CamperBot
@camperbot
Nov 13 2015 00:40

hint [8/9]

Second

function palindrome(str) {
  str = str.toLowerCase().replace(/[\W_]/g, '');
  for(var i = 0, len = str.length - 1; i < len/2; i++) {
    if(str[i] !== str[len-i]) {
      return false;
    }
  }
  return true;
}

Code Explanation:

We use regular expressions to replace any uppercase letter into a lowercase. Then we check if the string is the same as the reversed string using split() to split the original string by characters, then reverse and then join it back together.

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Yosafat Ariel
@yoskakomba
Nov 13 2015 00:41
hint
CamperBot
@camperbot
Nov 13 2015 00:41

hint [9/9]

Recursive Solution

function palindrome(str) {
// make all letters lowercase and remove non-alphanumeric characters
  str = str.toLowerCase();
  str = str.replace(/[^a-z|1-9]/g, "");

  // if the length of the string is 0 then it is a palindrome
  if (str.length === 0){
    return true;
  }
  // if the first letter and the last letter of the string do not equal eachother then it is not a palindrome
  if (str[0] !== str[str.length-1]){
    return false;
  }
  //Else, run the function without the first and last characters.
  else{
    return palindrome(str.slice(1,str.length - 1));
  }
}

Credits:

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