transmutable/lib/diff.js

immutable objects that pretend to be mutable

'use strict';

var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }

var _require = require('./symbols'),
    MUTATION = _require.MUTATION;

module.exports = function diff(a, b) {
    if (a && (typeof a === 'undefined' ? 'undefined' : _typeof(a)) == 'object' && b && (typeof b === 'undefined' ? 'undefined' : _typeof(b)) == 'object') {

        if (Array.isArray(a) && Array.isArray(b)) {
            var areSame = a.length == b.length && a.every(function (item, i) {
                return diff(item, b[i]) === undefined;
            });

            if (!areSame) {
                return _defineProperty({}, MUTATION, {
                    value: b
                });
            }
        }
        var keys = Object.keys(b).concat(Object.keys(a));
        var patch = {};
        keys.forEach(function (k) {

            var deeperPatch = diff(a[k], b[k]);
            if (deeperPatch) patch[k] = deeperPatch;
        });

        return Object.keys(patch).length ? patch : undefined;
    }
    if (a !== b) {
        return _defineProperty({}, MUTATION, {
            value: b
        });
    }
};