Validate your configurations with precise error messages:
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Define schema with validators which are agnostic to the actual representation of data, be it a JSON string, object in memory or any other format.
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Use schema with runners specific for formats (object and JSON5 runners are included). Get error messages with precise info (line and column numbers for example).
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Get the result of a validation as an object: either a plain JSON or some domain specific classes if schema is defined in that way.
Table of Contents
% npm install validated
Schema is defined with validators which are agnostic to the actual representation of data, be it a JSON string or an object in memory:
import {
mapping, sequence, object, partialObject, oneOf, maybe, enumeration, ref,
any, string, number, boolean
} from 'validated/schema'
There's schema validator for JSON objects in memory:
import {
validate as validateObject
} from 'validated/object'
And schema validator for strings with JSON/JSON5 encoded data:
import {
validate as validateJSON5
} from 'validated/json5'
Let's define some schema first:
let person = object({
name: string,
age: number,
})
let pet = object({
nickName: string,
age: number,
})
let collection = sequence(oneOf(person, pet))
validateJSON5(collection, '[{name: "John", age: 26}, {nickName: "Tima", age: 3}]')
// => [ { name: 'John', age: 26 }, { nickName: 'Tima', age: 3 } ]
validateObject(collection, [{name: "John", age: 26}, {nickName: "Tima", age: 3}])
// => [ { name: 'John', age: 26 }, { nickName: 'Tima', age: 3 } ]
Validates any value but not undefined or null:
validateObject(any, 'ok')
// => 'ok'
validateObject(any, 42)
// => 42
validateObject(any, null)
// ValidationError: Expected a value but got null
validateObject(any, undefined)
// ValidationError: Expected a value but got undefined
If you want to validated any value and even an absence of one then wrap it in
maybe:
validateObject(maybe(any), null)
// => null
validateObject(maybe(any), undefined)
// => undefined
Validate strings, numbers and booleans correspondingly.
validateObject(string, 'ok')
// => 'ok'
validateObject(number, 42)
// => 42
validateObject(boolean, true)
// => true
Validate enumerations:
validateObject(enumeration('yes', 'no'), 'yes')
// => 'yes'
validateObject(enumeration('yes', 'no'), 'no')
// => 'no'
validateObject(enumeration('yes', 'no'), 'oops')
// ValidationError: Expected value to be one of "yes", "no" but got "oops"
Validate mappings from string keys to values.
Untyped values (value validator defaults to any):
validateObject(mapping(), {})
// => {}
validateObject(mapping(), {a: 1, b: 'ok'})
// => { a: 1, b: 'ok' }
validateObject(mapping(), 'oops')
// ValidationError: Expected a mapping but got string
Typed value:
validateObject(mapping(number), {a: 1})
// => { a: 1 }
validateObject(mapping(number), {a: 1, b: 'ok'})
// ValidationError: Expected value of type number but got string
// While validating value at key "b"
Validate sequences.
Untyped values (value validator defaults to any):
validateObject(sequence(), [])
// => []
validateObject(sequence(), [1, 2, 'ok'])
// => [ 1, 2, 'ok' ]
validateObject(sequence(), 'oops')
// ValidationError: Expected an array but got string
Typed value:
validateObject(sequence(number), [1, 2])
// => [ 1, 2 ]
validateObject(sequence(number), [1, 2, 'ok'])
// ValidationError: Expected value of type number but got string
// While validating value at index 2
Validate objects, objects must specify validator for each of its keys:
let person = object({
name: string,
age: number,
})
validateObject(person, {name: 'john', age: 27})
// => { name: 'john', age: 27 }
validateObject(person, {name: 'john'})
// ValidationError: Expected value of type number but got undefined
// While validating missing value for key "age"
validateObject(person, {name: 'john', age: 'notok'})
// ValidationError: Expected value of type number but got string
// While validating value at key "age"
validateObject(person, {name: 'john', age: 42, extra: 'oops'})
// ValidationError: Unexpected key: "extra"
// While validating key "extra"
validateObject(person, {nam: 'john', age: 42})
// ValidationError: Unexpected key: "nam", did you mean "name"?
// While validating key "nam"
If some key is optional, wrap its validator in maybe:
let person = object({
name: string,
age: number,
nickName: maybe(string),
})
validateObject(person, {name: 'john', age: 27})
// => { name: 'john', age: 27 }
validateObject(person, {name: 'john', age: 27, nickName: 'J'})
// => { name: 'john', age: 27, nickName: 'J' }
You can also specify default values for keys:
let person = object({
name: string,
age: number,
nickName: string,
}, {
nickName: 'John Doe'
})
validateObject(person, {name: 'john', age: 27})
// => { name: 'john', age: 27, nickName: 'John Doe' }
validateObject(person, {name: 'john', age: 27, nickName: 'J'})
// => { name: 'john', age: 27, nickName: 'J' }
Validate a subset of the keys from the object, passing all extra keys through:
let person = partialObject({
name: string,
age: number,
})
validateObject(person, {name: 'john', age: 27})
// => { name: 'john', age: 27 }
validateObject(person, {name: 'john', age: 42, extra: 'ok'})
// => { name: 'john', age: 42, extra: 'ok' }
Validates null and undefined but passes through any other value to the
underlying validator:
validateObject(maybe(string), null)
// => null
validateObject(maybe(string), undefined)
// => undefined
validateObject(maybe(string), 'ok')
// => 'ok'
validateObject(maybe(string), 42)
// ValidationError: Expected value of type string but got number
Tries a multiple validators and choose the one which succeeds first:
validateObject(oneOf(string, number), 'ok')
// => 'ok'
validateObject(oneOf(string, number), 42)
// => 42
validateObject(oneOf(string, number), true)
// ValidationError: Either:
//
// Expected value of type string but got boolean
//
// Expected value of type number but got boolean
//
Allows to define recursive validators:
let node = ref()
let tree = object({value: any, children: maybe(sequence(node))})
node.set(tree)
validateObject(tree, {value: 'ok'})
// => { value: 'ok' }
validateObject(tree, {value: 'ok', children: [{value: 'child'}]})
// => { value: 'ok', children: [ { value: 'child' } ] }
Example:
class Point {
constructor(x, y) {
this.x = x
this.y = y
}
}
let point = sequence(number).andThen((value, error) => {
if (value.length !== 2) {
throw error('Expected an array of length 2 but got: ' + value.length)
}
return new Point(value[0], value[1])
})
validateObject(point, [1, 2])
// => Point { x: 1, y: 2 }
validateJSON5(point, '[1, 2]')
// => Point { x: 1, y: 2 }
validateJSON5(point, '[1]')
// ValidationError: Expected an array of length 2 but got: 1 (line 1 column 1)
Example:
import {Node} from 'validated/schema'
class Point {
constructor(x, y) {
this.x = x
this.y = y
}
}
class PointNode extends Node {
validate(context) {
// prevalidate value with primitive validators
let prevalidator = sequence(number)
let {value, context: nextContext} = prevalidator.validate(context)
// perform additional validations
if (value.length !== 2) {
// just report an error, context information such as line/column
// numbers will be injected automatically
throw context.error('Expected an array of length 2 but got: ' + value.length)
}
// construct a Point object, do whatever you want here
let [x, y] = value
let point = new Point(x, y)
// return constructed value and the next context
return {value: point, context: nextContext}
}
}
validateObject(new PointNode(), [1, 2])
// => Point { x: 1, y: 2 }
validateJSON5(new PointNode(), '[1, 2]')
// => Point { x: 1, y: 2 }
validateJSON5(new PointNode(), '[1]')
// ValidationError: Expected an array of length 2 but got: 1 (line 1 column 1)
Validated library uses FlowType extensively. Its API is defined in a way which automatically infers types for produced values:
import {object, string, number} from 'validated/schema'
import {validate} from 'validated/json5'
let personSchema = object({
name: string,
age: number,
})
let value: {name: string; age: number} = validate(
personSchema,
'{"name": "Andrey", age: 29}'
)Note that the type annotation isn't needed — FlowType infers the type automatically based on a schema.