index.js

function group_perms_by_model(permissions) {
  /*
    Groups an array of permissions objects by model.

    `permissions` is an array of objects, each of which contains `content_type` attribute
    which in turn has a `model` attribute.
    Example:
      Input: [
        {attr_1x, attr_2x, content_type: {model: m1}},
        {attr_1y, attr_2y, content_type: {model: m1}},
        {attr_1z, attr_2z, content_type: {model: m1}},
        {attr_1w, attr_2w, content_type: {model: m2}}
      ]

      Output:
        [
          {
            model: m1,
            perms: [
              {attr_1x, attr_2x, content_type: {model: m1}},
              {attr_1y, attr_2y, content_type: {model: m1}},
              {attr_1z, attr_2z, content_type: {model: m1}},
            ]
          },
          {
            model: m2,
            perms: [
              {attr_1w, attr_2w, content_type: {model: m2}},
            ]
          },
        ]
  */
  let groups = permissions.map((item) => item.content_type.get('model')),
    result = [];

  groups = new Set(groups);

  groups.forEach((model) => {
    let perms = permissions.filter(
      (item) => item.content_type.get('model') === model
    );
    result.push({ model, perms }); // same as result.push({mode: model, perms: perms})
  });

  return result;
}

function are_sets_equal(set1, set2) {
  /*
    Returns `true` if given sets are equal and `false` otherwise.

    `set1` and `set2` are expected to be instances of javascript `Set`
    class.
  */
  let same_size, same_values;

  same_size = (a, b) => a.size === b.size;
  same_values = (a, b) => [...a].every((value) => b.has(value));

  return same_size(set1, set2) && same_values(set1, set2);
}

export { group_perms_by_model, are_sets_equal };