Assert

Helper functions that have to do with asserting.

Functions

assertArray()

function assertArray<T>(
  value,
  ...__namedParameters
): asserts value is T & unknown[];

Defined in: functions/assert.ts:17

Helper function to throw an error if the provided value is not an array.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [readonly unknown[]] ? ["The assertion is useless because the provided value is already an array."] : [string]

Returns

asserts value is T & unknown[]

---

assertArrayBoolean()

function assertArrayBoolean<T>(
  value,
  ...__namedParameters
): asserts value is T & boolean[];

Defined in: functions/assert.ts:34

Helper function to throw an error if the provided value is not an array with every element being a boolean.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [readonly boolean[]] ? ["The assertion is useless because the provided value is already a boolean array."] : [string]

Returns

asserts value is T & boolean[]

---

assertArrayLength()

Call Signature

function assertArrayLength<E, N>(
  value,
  length,
  msg,
): asserts value is Tuple<E, N>;

Defined in: functions/assert.ts:55

Helper function to throw an error if the provided array does not have the specified length. Will also type narrow the array into a tuple of the specified length.

Type Parameters

Type Parameter
E
N extends number

Parameters

Parameter	Type
value	E[]
length	N
msg	string

Returns

asserts value is Tuple<E, N>

Call Signature

function assertArrayLength<E, N>(
  value,
  length,
  msg,
): asserts value is Readonly<Tuple<E, N>>;

Defined in: functions/assert.ts:60

Helper function to throw an error if the provided array does not have the specified length. Will also type narrow the array into a tuple of the specified length.

Type Parameters

Type Parameter
E
N extends number

Parameters

Parameter	Type
value	readonly E[]
length	N
msg	string

Returns

asserts value is Readonly<Tuple<E, N>>

---

assertArrayNonEmpty()

function assertArrayNonEmpty<T>(
  value,
  ...__namedParameters
): asserts value is T
  & (T extends readonly E[] ? [E, ...E[]] : [unknown, ...unknown[]]);

Defined in: functions/assert.ts:76

Helper function to throw an error if the provided value is not an array or is an empty array.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [readonly [unknown, unknown]] ? ["The assertion is useless because the provided value is already a non-empty array."] : [string]

Returns

asserts value is T & (T extends readonly E[] ? [E, ...E[]] : [unknown, ...unknown[]])

---

assertArrayNumber()

function assertArrayNumber<T>(
  value,
  ...__namedParameters
): asserts value is T & number[];

Defined in: functions/assert.ts:98

Helper function to throw an error if the provided value is not an array with every element being a number.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [readonly number[]] ? ["The assertion is useless because the provided value is already a number array."] : [string]

Returns

asserts value is T & number[]

---

assertArrayObject()

function assertArrayObject<T>(
  value,
  ...__namedParameters
): asserts value is T & Record<string, unknown>[];

Defined in: functions/assert.ts:119

Helper function to throw an error if the provided value is not an array with every element being an object (i.e., a TypeScript record).

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [readonly Record<string, unknown>[]] ? ["The assertion is useless because the provided value is already an object array."] : [string]

Returns

asserts value is T & Record<string, unknown>[]

---

assertArrayString()

function assertArrayString<T>(
  value,
  ...__namedParameters
): asserts value is T & string[];

Defined in: functions/assert.ts:140

Helper function to throw an error if the provided value is not an array with every element being a string.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [readonly string[]] ? ["The assertion is useless because the provided value is already a string array."] : [string]

Returns

asserts value is T & string[]

---

assertBoolean()

function assertBoolean<T>(
  value,
  ...__namedParameters
): asserts value is T & boolean;

Defined in: functions/assert.ts:158

Helper function to throw an error if the provided value is not a boolean.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [boolean] ? ["The assertion is useless because the provided value is already a boolean."] : [string]

Returns

asserts value is T & boolean

---

assertDefined()

function assertDefined<T>(
  value,
  ...__namedParameters
): asserts value is Exclude<T, undefined>;

Defined in: functions/assert.ts:176

Helper function to throw an error if the provided value is equal to undefined.

This is useful to have TypeScript narrow a T | undefined value to T in a concise way.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[undefined] extends [T] ? [string] : ["The assertion is useless because the provided value does not contain undefined."]

Returns

asserts value is Exclude<T, undefined>

---

assertEnumValue()

function assertEnumValue<T>(
  value,
  transpiledEnum,
  msg,
  set?,
): asserts value is T[keyof T];

Defined in: functions/assert.ts:199

Helper function to throw an error if the provided value is not contained within an enum.

Type Parameters

Type Parameter
T extends TranspiledEnum

Parameters

Parameter	Type	Description
value	string | number	The value to check.
transpiledEnum	T	The enum to check against.
msg	string	The error message to throw if the check fails.
set?	ReadonlySet<string | number>	Optional. A set that contains all of the values of an enum. If provided, this function will check for existence using the set (instead of the enum itself). Using a set should be more performant for enums with around 52 or more elements.

Returns

asserts value is T[keyof T]

---

assertInteger()

function assertInteger(value, msg): asserts value is number;

Defined in: functions/assert.ts:211

Helper function to throw an error if the provided value is not an integer.

Parameters

Parameter	Type
value	unknown
msg	string

Returns

asserts value is number

---

assertIs()

function assertIs<T>(value, constructor, msg): asserts value is InstanceType<T>;

Defined in: functions/assert.ts:227

Helper function to throw an error if the provided value is not an instance of the expected class.

This is useful to have TypeScript narrow a value to a specific type in a concise way.

Type Parameters

Type Parameter
T extends (…args) => unknown

Parameters

Parameter	Type
value	unknown
constructor	T
msg	string

Returns

asserts value is InstanceType<T>

---

assertNotNull()

function assertNotNull<T>(
  value,
  ...__namedParameters
): asserts value is Exclude<T, null>;

Defined in: functions/assert.ts:244

Helper function to throw an error if the provided value is equal to null.

This is useful to have TypeScript narrow a T | null value to T in a concise way.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[null] extends [T] ? [string] : ["The assertion is useless because the provided value does not contain null."]

Returns

asserts value is Exclude<T, null>

---

assertNumber()

function assertNumber<T>(
  value,
  ...__namedParameters
): asserts value is T & number;

Defined in: functions/assert.ts:258

Helper function to throw an error if the provided value is not a number.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [number] ? ["The assertion is useless because the provided value is already a number."] : [string]

Returns

asserts value is T & number

---

assertObject()

function assertObject<T>(
  value,
  ...__namedParameters
): asserts value is T & Record<string, unknown>;

Defined in: functions/assert.ts:280

Helper function to throw an error if the provided value is not an object (i.e., a TypeScript record).

This is useful to have TypeScript narrow a Record<string, unknown> | undefined value to Record<string, unknown> in a concise way.

Under the hood, this function uses the isObject helper function.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [Record<string, unknown>] ? ["The assertion is useless because the provided value is already an object."] : [string]

Returns

asserts value is T & Record<string, unknown>

---

assertPositiveInteger()

function assertPositiveInteger(value, msg): asserts value is number;

Defined in: functions/assert.ts:294

Helper function to throw an error if the provided value is not a positive integer.

Parameters

Parameter	Type
value	unknown
msg	string

Returns

asserts value is number

---

assertString()

function assertString<T>(
  value,
  ...__namedParameters
): asserts value is T & string;

Defined in: functions/assert.ts:306

Helper function to throw an error if the provided value is not a string.

Type Parameters

Type Parameter
T

Parameters

Parameter	Type
value	T
…__namedParameters	[T] extends [string] ? ["The assertion is useless because the provided value is already a string."] : [string]

Returns

asserts value is T & string

---

assertStringNotEmpty()

function assertStringNotEmpty(value, msg): asserts value is string;

Defined in: functions/assert.ts:320

Helper function to throw an error if the provided value is not a string or an empty string.

Parameters

Parameter	Type
value	unknown
msg	string

Returns

asserts value is string