code: function unique(array) {
    const results = [];
  
    for (let idx = 0, len = array.length; idx < len; idx++) {
      if (!contains(results, array[idx])) {
        results.push(array[idx]);
      }
    }
  
    return results;
  }
docs: produces a duplicate-free version of the array
  
  @param {Array} array