code: function includes(array, element) {
    if (!array) {
      return false;
    }
  
    const length = array.length;
  
    for (let i = 0; i < length; i++) {
      if (array[i] === element) {
        return true;
      }
    }
  
    return false;
  }
docs: Polyfill for Array.prototype.includes for Node.js < 6