sindresorhus/is · error · TypeError

Expected value which is `Int16Array`, received value of type

Error message

Expected value which is `Int16Array`, received value of type `${is(value)}`.

What it means

Thrown by `assertInt16Array()` when `isInt16Array()` fails — the value is not a genuine Int16Array instance. The check is by internal tag, so structurally similar values (plain arrays, other typed-array element types) are rejected.

Source

Thrown at source/index.ts:1677

		throw new TypeError(message ?? typeErrorMessage('HTMLElement', value));
	}
}

export function assertInfinite(value: unknown, message?: string): asserts value is number {
	if (!isInfinite(value)) {
		throw new TypeError(message ?? typeErrorMessage('infinite number', value));
	}
}

export function assertInRange(value: number, range: number | [number, number], message?: string): asserts value is number {
	if (!isInRange(value, range)) {
		throw new TypeError(message ?? typeErrorMessage('in range', value));
	}
}

export function assertInt16Array(value: unknown, message?: string): asserts value is Int16Array {
	if (!isInt16Array(value)) {
		throw new TypeError(message ?? typeErrorMessage('Int16Array', value));
	}
}

export function assertInt32Array(value: unknown, message?: string): asserts value is Int32Array {
	if (!isInt32Array(value)) {
		throw new TypeError(message ?? typeErrorMessage('Int32Array', value));
	}
}

export function assertInt8Array(value: unknown, message?: string): asserts value is Int8Array {
	if (!isInt8Array(value)) {
		throw new TypeError(message ?? typeErrorMessage('Int8Array', value));
	}
}

export function assertInteger(value: unknown, message?: string): asserts value is number {
	if (!isInteger(value)) {
		throw new TypeError(message ?? typeErrorMessage('integer', value));

View on GitHub ↗ (pinned to 7821031c66)

Solutions

Wrap the source in the right view: `new Int16Array(arrayBuffer)` or `Int16Array.from(plainArray)`.
Double-check signedness — if the producer emits Uint16Array, either reinterpret the buffer (`new Int16Array(u16.buffer)`) or change the assertion to match the actual type.
For Node Buffers, create a view over the underlying memory: `new Int16Array(buf.buffer, buf.byteOffset, buf.byteLength / 2)`.

Example fix

// before
ws.onmessage = e => { assertInt16Array(e.data); }; // ArrayBuffer
// after
ws.onmessage = e => {
  const samples = new Int16Array(e.data);
  assertInt16Array(samples);
};

Defensive patterns

Strategy: type-guard

Validate before calling

if (!(value instanceof Int16Array)) {
  throw new TypeError(`Expected Int16Array, got ${typeof value}`);
}

Type guard

function isInt16Array(value: unknown): value is Int16Array {
  return value instanceof Int16Array;
}

Try / catch

try {
  assert.int16Array(value);
} catch (error) {
  if (error instanceof TypeError) { /* convert with Int16Array.from or reject */ }
  else throw error;
}

Prevention

Convert explicitly with `Int16Array.from(arr)` or `new Int16Array(buffer)` — plain arrays and other typed-array kinds fail
Uint16Array and Int16Array are distinct despite identical element size; keep signedness straight in signatures
Use the library's cross-realm-safe `is.int16Array` when values may come from workers or iframes

When it happens

Trigger: `is.assert.int16Array(value)` with a Uint16Array, Int8Array, plain `number[]`, ArrayBuffer, DataView, or Node Buffer.

Common situations: Audio/binary-protocol code confusing signed and unsigned 16-bit views (Int16Array vs Uint16Array — a very common mix-up for PCM audio); receiving raw ArrayBuffers from WebSocket/fetch and forgetting to wrap them; serialized data arriving as plain arrays.

Related errors

AI-assisted analysis of sindresorhus/is@7821031c66 (2026-07-31). Data as JSON: /data/errors/a522f7fad154ada5.json. Report an issue: GitHub ↗.