Refinements
Superstruct allows you to constrain existing structs with further validation. This doesn't change the type of the struct, but simply introduces extra validation logic. This can be useful for example when ensuring that a string matches a specific
RegExp
.empty(string())
empty(array())
''
[]
empty
enforces that a string
, array
, map
, or set
is empty.🤖 Technically this is the same as usingsize
of zero, but "empty" feels slightly nicer and will give a slightly easier to read error.
max(number(), 0)
-1
max
enforces that a number
struct is less than a threshold.🤖 If you need an exclusive maxmimum you can pass{ exclusive: true }
as the third argument, likemax(number(), 0, { exclusive: true })
for negative numbers.
min(number(), 9000)
9001
min
enforces that a number
struct is greater than a threshold.🤖 If you need an exclusive minimum you can pass{ exclusive: true }
as the third argument, likemin(number(), 0, { exclusive: true })
for positive numbers.
nonempty(string())
nonempty(array())
nonempty
enforces that a string, array, map, or set is not empty. This does the opposite of empty
.pattern(string(), /\d+/)
'123'
pattern
enforces that a string
struct also matches a supplied RegExp
.size(string(), 1, 100)
size(array(number()), 0)
size(number(), 93, Infinity)
'a string of text'
[]
Infinity
size
enforces that a number
, string
, array
, map
, or set
struct also is within a certain min
and max
size (or length).🤖 Themax
argument is optional and defaults to whatever you pass formin
, which makes specifying exact sizes easy (just omit the max).
You can also define your own custom refinments that are specific to your application's requirements, like so:
import { number, refine } from 'superstruct'
const Positive = refine(number(), 'positive', (value) => value >= 0)
This allows you to define more fine-grained runtime validation, while still preserving the
number
type at compile time.🤖 Thevalue
provided to the refiner function is guaranteed to be the provided struct's type. This means you can layer additional validation on top of even complex structs with minimal hassle.
If you'd like to customize the error message that will be returned/thrown by your struct when a value doesn't pass your refinement's validation, you can return a string instead of a boolean inside the refiner.
const DateRange = refine(
object({
startDate: number(),
endDate: number(),
}),
'DateRange',
(value) => {
if (value.startDate < value.endDate) {
return true
}
// Returning a string indicates that validation failed and the provided
// string should be used as a custom error message.
return (
`Expected 'startDate' to be less than 'endDate' on type 'DateRange', ` +
`but received ${JSON.stringify(value)}`
)
}
)
Last modified 1yr ago