docs: function assignDefaults(defaults, options) {
    var keys = Object.keys(defaults),
        i = keys.length,
        k;
  
    options = options || {};
  
    while (i--) {
      k = keys[i];
      if (!(k in options)) {
        options[k] = defaults[k];
      }
    }
  
    return options;
  }