I’m puzzled with a validator while trying express.

An optional parameter I receive to my route, flags, should either be an integer or an array of integers.

The array of integers part is checked with the help of a custom validator chained after isArray().

Below is my validating code, and examples of data it lets in.

                oneOf([
                    body("flags").isInt(),
                    body("flags")
                        .optional()
                        .isArray()
                        .custom((value) => {
                            //return value.every(Number.isInteger);
                            if (!value.every(Number.isInteger)) {
                                throw new Error('permissionFlags should contain Integers only');
                            }
                            return true;
                        }),
                ], {
                    message: 'it should be an integer or an array of integers',
                }),

All the following sorts of values are being let in, however the first one isn’t an array of integers.

flags: [ 8, 1, 'WRONG_PERMISSION' ] // this is not an int, neither an array of integers.

flags: [ 8, 1 ]

flags: 8

A big thank in advance for a good advice.