text: function isPangram(string) {
      let letters = [];
      let strArr = string.toLowerCase().split('');
      for (let i = 97; i < 123; i++) {
          letters.push(String.fromCharCode(i));
      }
      for (let letter of letters) {
          if (!strArr.includes(letter)) return false;
      }
      return true;
  }