kurple-palindrome/index.js

Palindrome detector

module.exports = Phrase;

// Adds `reverse` to all strings.
String.prototype.reverse = function() {
  return Array.from(this).reverse().join("");
}

// Defines a Phrase object.
function Phrase(content) {
  this.content = content;

  // Returns content processed for palindrome testing.
  this.processedContent = function processedContent() {
    return this.letters().toLowerCase();
  }

  // Returns the letters in the content.
  // For example:
  //   new Phrase("Hello, world!").letters() === "Helloworld"
  this.letters = function letters() {
    const lettersRegEx = /[a-z]/i;
    return Array.from(this.content).filter(c => c.match(lettersRegEx)).join("");
  }

  // Returns true if the phrase is a palindrome, false otherwise.
  this.palindrome = function palindrome() {
    if (this.letters()) {
      return this.processedContent() === this.processedContent().reverse();
    } else {
      return false;
    }
  }
}