deepDiffObj, Function to analyze two objects and return if there were changes, if there were not, if something was deleted etc.

deepDiffObj.js

const deepDiffMapper = function () {
    return {
        VALUE_CREATED: 'created',
        VALUE_UPDATED: 'updated',
        VALUE_DELETED: 'deleted',
        VALUE_UNCHANGED: 'unchanged',
        map: function (obj1, obj2) {
            if (this.isFunction(obj1) || this.isFunction(obj2)) {
                throw 'Invalid argument. Function given, object expected.';
            }
            if (this.isValue(obj1) || this.isValue(obj2)) {
                let returnObj = {
                    type: this.compareValues(obj1, obj2),
                    original: obj1,
                    updated: obj2,
                };
                // if (returnObj.type != this.VALUE_UNCHANGED) {
                //     return returnObj;
                // }
                // return undefined;
                return returnObj;
            }

            var diff = {};
            let foundKeys = {};
            for (var key in obj1) {
                if (this.isFunction(obj1[key])) {
                    continue;
                }

                var value2 = undefined;
                if (obj2[key] !== undefined) {
                    value2 = obj2[key];
                }

                let mapValue = this.map(obj1[key], value2);
                foundKeys[key] = true;
                if (mapValue) {
                    diff[key] = mapValue;
                }
            }
            for (var key in obj2) {
                if (this.isFunction(obj2[key]) || foundKeys[key] !== undefined) {
                    continue;
                }

                let mapValue = this.map(undefined, obj2[key]);
                if (mapValue) {
                    diff[key] = mapValue;
                }
            }

            //2020-06-13: object length code copied from https://stackoverflow.com/a/13190981/2336212
            if (Object.keys(diff).length > 0) {
                return diff;
            }
            return undefined;
        },
        compareValues: function (value1, value2) {
            if (value1 === value2) {
                return this.VALUE_UNCHANGED;
            }
            if (this.isDate(value1) && this.isDate(value2) && value1.getTime() === value2.getTime()) {
                return this.VALUE_UNCHANGED;
            }
            if (value1 === undefined) {
                return this.VALUE_CREATED;
            }
            if (value2 === undefined) {
                return this.VALUE_DELETED;
            }
            return this.VALUE_UPDATED;
        },
        isFunction: function (x) {
            return Object.prototype.toString.call(x) === '[object Function]';
        },
        isArray: function (x) {
            return Object.prototype.toString.call(x) === '[object Array]';
        },
        isDate: function (x) {
            return Object.prototype.toString.call(x) === '[object Date]';
        },
        isObject: function (x) {
            return Object.prototype.toString.call(x) === '[object Object]';
        },
        isValue: function (x) {
            return !this.isObject(x) && !this.isArray(x);
        }
    }
}();

// Calling
deepDiffMapper.map({_id: 1, descricao: 'teste'}, {_id: 1, descricao: 'teste 2'})
// Return
/*{
   "_id":{
      "type":"unchanged",
      "original":1,
      "updated":1
   },
   "descricao":{
      "type":"updated",
      "original":"teste",
      "updated":"teste 2"
   }
}*/