Palindrome for your Dome

Author: dwqs

codewars/palindrome-for-your-dome.md

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+#Description
+
+A palindrome is a word, phrase, number, or other sequence of symbols or elements, whose meaning may be interpreted the same way in either forward or reverse direction. Famous examples include "Amore, Roma", "A man, a plan, a canal: Panama" and "No 'x' in 'Nixon'". - wikipedia
+
+Our goal is to determine whether or not a given string is a valid palindrome or not.
+
+Like the above examples, here are a few test cases which are also populated:
+
+```
+"Amore, Roma" => valid
+"A man, a plan, a canal: Panama" => valid
+"No 'x' in 'Nixon'" => valid
+"Abba Zabba, you're my only friend" => invalid
+```
+
+You can see that they are case insensitive and disregards non alphanumeric characters. In addition to a few predefined tests, your function will also be tested against a random string generator 50 times which are guaranteed to produce valid palindromes.
+
+NOTE: reverse/reverse! have been disabled for String/Array and reverse() for JS.
+
+#Best practice
+
+**First:**
+```
+function palindrome(string) {
+ var sanitized = string.replace(/[^A-Za-z]/g, "").toLowerCase();
+ return sanitized == sanitized.split("").reduceRight(function(sum, v) {return sum + v;});
+}
+```
+
+**Second:**
+```
+function palindrome(string) {
+ var s = string.replace(/[^A-Za-z0-9]/g, "").toLowerCase();
+ for (var i = 0; i < s.length/2; i++) if (s[i] != s[s.length-i-1]) return false;
+ return true;
+}
+```
+
+**Third:**
+```
+function palindrome(string) {
+ var s = string.toLowerCase().replace(/[^a-z0-9]+/g, '');
+ return s == s.split('').reduce(function(str, value) {
+ return value+str;
+ }, '');
+}
+```
+
+**Fourth:**
+```
+function palindrome(string) {
+ return string.toLowerCase().replace(/[^a-z]/gi,'').split('').every(function(a,b,c){
+ return a===c[c.length-b-1]
+ })
+}
+```
+
+**Fifth:**
+```
+function palindrome(string) {
+ return string
+ .toLowerCase()
+ .replace(/[^a-z]/g,'')
+ .split("")
+ .every(function(v, i, array){ return v == array[array.length-i-1] })
+ ;
+}
+```
+
+Kata's link: [Palindrome for your Dome](http://www.codewars.com/kata/palindrome-for-your-dome/)

summary.md

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-[Sum of many ints](codewars/sum-of-many-ints.md);
+[Sum of many ints](codewars/sum-of-many-ints.md)
+[Palindrome for your Dome](codewars/palindrome-for-your-dome.md)