A collection of composable JavaScript runtime type predicates with TypeScript type guard declarations
Isntnt is a collection of composable JavaScript runtime type predicates with TypeScript type guard declarations. Supports generics including union and intersection types.
(floor: number) => (value: unknown) => value is number``typescript`
const isAboveZero = above(0)
typescript
const isBetween0And21 = and(above(0), below(21))const isUser = shape({ name: isString })
const hasEmailAddress = at('email', isString)
const isUserWithEmail = and(isUser, hasEmailAddress) // (value: unknown) => { name: string } & { email: string }
`array
typescript
const isAnyArray = array(isAny) // (value: unknown) => value is Array
`at
typescript
const isAnyAtFoo = at('foo', isAny) // (value: unknown) => value is { foo: any }
`below
typescript
const isBelow21 = below(21)
`either
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const isFooOrBar = either('foo', 'bar') // (value: unknown) => value is 'foo' | 'bar'
`has
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const hasFoo = has('foo') // (value: unknown) => value is { 'foo': unknown }
`instance
typescript
const isInstanceofString = instance(String) // (value: unknown) => value is String
`literal
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const is42 = literal(42) // (value: unknown) => value is 42
`max
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const isMax255 = max(255)
`maybe
typescript
const isMaybeString = maybe(isString) // (value: unknown) => value is string | null | undefined
`min
typescript
const isMin18 = min(18)
`noneable
nullable
typescript
const isNullableString = nullable(isString) // (value: unknown) => value is string | null
`object
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const isEnum = object(isUint) // (value: unknown) => value is Record
`optional
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const isOptionalString = optional(isString) // (value: unknown) => value is string | undefined
`or
typescript
const isStringOrNumber = or(isString, isNumber) // (value: unknown) => value is string | number
`record
typescript
const isDictionary = record(isString, isInt) // (value: unknown) => value is Record
`shape
> Note: Actual signature also considers optional members (
) in its Predicate type`typescript
const isCoordinate = shape({ x: isNumber, y: isNumber }) // (value: unknown) => value is { x: number, y: number }
`test
typescript
const isSlug = test(/^[\w-]+$/)
`tuple
typescript
const isPoint = tuple(isNumber, isNumber) // (value: unknown) => value is [number, number]
`Predicates
isAny
Always returns
.`typescript
isAny(value)
`isArray
typescript
isArray(value)
`isArrayLike
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isArrayLike(value)
`isBigInt
typescript
isBigInt(value)
`isBoolean
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isBoolean(value)
`isDate
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isDate(value)
`isDictionary
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isDictionary(value)
`isFalse
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isFalse(value)
`isFunction
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isFunction(value)
`isInt
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isInt(value)
`isInt8
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isInt8(value)
`isInt16
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isInt16(value)
`isInt32
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isInt32(value)
`isLength
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isLength(value)
`isMap
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isMap(value)
`isNegative
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isNegative(value)
`isNever
Always returns
;`typescript
isNever(value)
`isNone
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isNone(value)
`isNull
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isNull(value)
`isNumber
typescript
isNumber(value)
`isObject
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isObject(value)
`isObjectLike
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isObjectLike(value)
`isPlainObject
typescript
isPlainObject(value)
`isPositive
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isPositive(value)
`isPrimitive
typescript
isPrimitive(value)
`
isRegExp
typescript
isRegExp(value)
`isSerializable
typescript
isSerializable(value)
`isSerializableArray
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isSerializableArray(value)
`isSerializableNumber
typescript
isSerializableNumber(value)
`isSerializableObject
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isSerializableObject(value)
`isSerializablePrimitive
typescript
isSerializablePrimitive(value)
`isSet
typescript
isSet(value)
`isSome
typescript
isSome(value)
`isString
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isString(value)
`isSymbol
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isSymbol(value)
`isTrue
typescript
isTrue(value)
`isUint
typescript
isUint(value)
`isUint8
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isUint8(value)
`isUint16
typescript
isUint16(value)
`isUint32
typescript
isUint32(value)
`isUndefined
typescript
isUndefined(value)
`isWeakMap
typescript
isWeakMap(value)
`isWithLength
typescript
isWithLength(value)
`Types
Intersect
typescript
Intersect // A & B
`Maybe
typescript
Maybe // T | null | undefined
`typescript
type MaybeString = Maybe // string | null | undefined
`None
typescript
None // null | undefined
`Nullable
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Nullable // T | null
`typescript
type NullableString = Nullable // string | null
`Optional
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Optional // T | undefined
`typescript
type OptionalString = Optional // string | undefined
`Predicate
typescript
Predicate // (value: unknown, ...rest: Array) => value is T
`Primitive
typescript
Primitive // null | undefined | boolean | number | string | symbol | bigint
`Serializable
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Serializable // SerializableArray | SerializableObject | SerializablePrimitive
`SerializableArray
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SerializableArray // Array
`SerializableObject
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SerializableObject // Partial<{ [key: string]: Serializable }>
`SerializablePrimitive
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SerializablePrimitive // null | boolean | number | string
`Some
typescript
Some // Function | boolean | bigint | number | string | symbol | object
Some // Exclude
`typescript
// Make sure T is not null or undefined
type Option = T | E// Remove
or undefined from a type
type MaybeString = Optional // string | null | undefined
type SomeString = Some // string
`Static
typescript
Static> // T
`typescript
type True = Static // true
``