extendable-immutable/es/extendable.js

Wraps around Immutable.js to turn it inheritable

import createExtendable from './util/createExtendable';

export default function extendable(Base) {
  var NAME = Base.prototype.constructor.name;
  var emptyBase = new Base();

  var exampleBase = void 0;
  if (emptyBase.add) {
    exampleBase = emptyBase.add('a');
  } else if (emptyBase.set) {
    exampleBase = emptyBase.set('a', 'b');
  } else if (emptyBase.push) {
    exampleBase = emptyBase.push('a');
  } else {
    throw new Error('extendable: `' + NAME + '` is not supported.');
  }

  var KEYS = Object.keys(exampleBase);
  var EMPTY = KEYS.reduce(function (acc, key) {
    acc[key] = emptyBase[key];
    return acc;
  }, {});

  function copy(val, update) {
    return KEYS.reduce(function (acc, key) {
      acc[key] = update[key];
      return acc;
    }, val);
  }

  function empty(val) {
    return Object.keys(EMPTY).reduce(function (acc, key) {
      acc[key] = EMPTY[key];
      return acc;
    }, val);
  }

  function ExtendableWrapper(val) {
    var instance = this;
    if (instance === undefined) {
      instance = new ExtendableWrapper(val);
    }

    return instance.__wrapImmutable(new Base(val));
  }

  ExtendableWrapper['is' + NAME] = function is(obj) {
    return obj && obj instanceof ExtendableWrapper;
  };

  ExtendableWrapper.prototype = createExtendable(Base, copy, empty);
  ExtendableWrapper.prototype.constructor = ExtendableWrapper;

  ExtendableWrapper.prototype.toString = function toString() {
    return 'Extendable.' + Base.prototype.toString.call(this);
  };

  return ExtendableWrapper;
}