freeCodeCamp/curriculum/challengeTitles.js

import _ from 'lodash';

class ChallengeTitles {
  constructor() {
    this.knownTitles = [];
  }
  check(title) {
    if (typeof title !== 'string') {
      throw new Error(`Expected a valid string for ${title}, but got a(n) ${typeof title}`);
    } else if (title.length === 0) {
      throw new Error(`Expected a title length greater than 0`);
    }
    const titleToCheck = title.toLowerCase().replace(/\s+/g, '');
    const isKnown = this.knownTitles.includes(titleToCheck);
    if (isKnown) {
      throw new Error(`
    All challenges must have a unique title.

    The title ${title} is already assigned
    `);
    }
    this.knownTitles = [ ...this.knownTitles, titleToCheck ];
  }
}

export default ChallengeTitles;