palindrome node js code example
Example 1: How do you detect whether or not a word is a palindrome in javascript
function palindrome(str) {
// Step 1. Lowercase the string and use the RegExp to remove unwanted characters from it
var re = /[\W_]/g; // or var re = /[^A-Za-z0-9]/g;
var lowRegStr = str.toLowerCase().replace(re, '');
// str.toLowerCase() = "A man, a plan, a canal. Panama".toLowerCase() = "a man, a plan, a canal. panama"
// str.replace(/[\W_]/g, '') = "a man, a plan, a canal. panama".replace(/[\W_]/g, '') = "amanaplanacanalpanama"
// var lowRegStr = "amanaplanacanalpanama";
// Step 2. Use the same chaining methods with built-in functions from the previous article 'Three Ways to Reverse a String in JavaScript'
var reverseStr = lowRegStr.split('').reverse().join('');
// lowRegStr.split('') = "amanaplanacanalpanama".split('') = ["a", "m", "a", "n", "a", "p", "l", "a", "n", "a", "c", "a", "n", "a", "l", "p", "a", "n", "a", "m", "a"]
// ["a", "m", "a", "n", "a", "p", "l", "a", "n", "a", "c", "a", "n", "a", "l", "p", "a", "n", "a", "m", "a"].reverse() = ["a", "m", "a", "n", "a", "p", "l", "a", "n", "a", "c", "a", "n", "a", "l", "p", "a", "n", "a", "m", "a"]
// ["a", "m", "a", "n", "a", "p", "l", "a", "n", "a", "c", "a", "n", "a", "l", "p", "a", "n", "a", "m", "a"].join('') = "amanaplanacanalpanama"
// So, "amanaplanacanalpanama".split('').reverse().join('') = "amanaplanacanalpanama";
// And, var reverseStr = "amanaplanacanalpanama";
// Step 3. Check if reverseStr is strictly equals to lowRegStr and return a Boolean
return reverseStr === lowRegStr; // "amanaplanacanalpanama" === "amanaplanacanalpanama"? => true
}
palindrome("A man, a plan, a canal. Panama");
Example 2: javascript palindrome
function remove_spaces_strict(string)
{
return string.replace(/\s/gm, "");
}
function to_lower_case(string="")
{
return string.toLocaleLowerCase();
}
function isPalindrome(string) {
let string1 = string;
if (typeof string === 'string' || typeof string === 'number') {
if (typeof string === 'number') {
string1 = new Number(string1).toString();
}
string1 = remove_spaces_strict(string1);
string1 = to_lower_case(string1);
let len1 = string1.length;
let len = Math.floor(string1.length / 2);
let i = 0;
while(i < len) {
if (string1[i] !== string1[len1 - (1 + i)]) {
return false;
}
console.log(string1[i] + " = " + string1[len1 - (1 + i)]);
i++;
}
}else{
throw TypeError(`Was expecting an argument of type string1 or number, recieved an argument of type ${ typeof string1}`);
}
return string;
}