immutable-js/src/util/fromJS.js

Immutable types in JavaScript

/**
 *  Copyright (c) 2015, Jan Biasi.
 *  All rights reserved.
 *
 *  This source code is licensed under the BSD-style license found in the
 *  LICENSE file in the root directory of this source tree. An additional grant
 *  of patent rights can be found in the PATENTS file in the same directory.
 */

import { KeyedSequence, IndexedSequence } from '../Sequence';
import { isNative } from '../Native';

export function fromJS(native, converter) {
    return converter ?
        fromJSWith(converter, native, '', {'': native}) :
        fromJSDefault(native);
}

function fromJSWith(converter, native, key, parent) {
    if(Array.isArray(native)) {
        return converter.call(parent, key, IndexedSequence(native).map((v, k) => {
            fromJSWith(converter, v, k, native);
        }));
    } else if(maybePlainObject(native)) {
        return converter.call(parent, key, KeyedSequence(native).map((v, k) => {
            fromJSWith(converter, v, k, native);
        }));
    }
}

function fromJSDefault(json) {
    if(Array.isArray(json)) {
        return IndexedSequence(json);
    }
    if(maybePlainObject(json)) {
        return KeyedSequence(json);
    }
}

function maybePlainObject(value) {
  return value && (value.constructor === Object || value.constructor === undefined);
}