palindrom program in js code example
Example 1: palindrome in javascript
function palindrome(str) {
var len = str.length;
var mid = Math.floor(len/2);
for ( var i = 0; i < mid; i++ ) {
if (str[i] !== str[len - 1 - i]) {
return false;
}
}
return true;
}
Example 2: javascript palindrome check
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");