Tell us what’s happening:
What’s the use of those both while statements in the second code??
Even in the first code we use the same method.
Is there only one difference that in one we start from the end and in the other we start from the middle?
Second Code
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;
}
Second Code
function palindrome(str) {
//assign a front and a back pointer
let front = 0;
let back = str.length - 1;
//back and front pointers won't always meet in the middle, so use (back > front)
while (back > front) {
//increments front pointer if current character doesn't meet criteria
while ( str[front].match(/[\W_]/) ) {
front++;
continue;
}
//decrements back pointer if current character doesn't meet criteria
while ( str[back].match(/[\W_]/) ) {
back--;
continue;
}
//finally does the comparison on the current character
if ( str[front].toLowerCase() !== str[back].toLowerCase() ) return false
front++;
back--;
}
//if the whole string has been compared without returning false, it's a palindrome!
return true;
}
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Link to the challenge:
https://www.freecodecamp.org/challenges/check-for-palindromes