sindresorhus/is · error · TypeError

Expected value which is `Uint8ClampedArray`, received value

Error message

Expected value which is `Uint8ClampedArray`, received value of type `${is(value)}`.

What it means

Thrown by `assertUint8ClampedArray()` in @sindresorhus/is when the value is not a Uint8ClampedArray. This type is distinct from Uint8Array (clamping vs wrapping arithmetic) and the check is exact — a plain Uint8Array fails it.

Source

Thrown at source/index.ts:1944

		throw new TypeError(message ?? typeErrorMessage('Uint16Array', value));
	}
}

export function assertUint32Array(value: unknown, message?: string): asserts value is Uint32Array {
	if (!isUint32Array(value)) {
		throw new TypeError(message ?? typeErrorMessage('Uint32Array', value));
	}
}

export function assertUint8Array(value: unknown, message?: string): asserts value is Uint8Array {
	if (!isUint8Array(value)) {
		throw new TypeError(message ?? typeErrorMessage('Uint8Array', value));
	}
}

export function assertUint8ClampedArray(value: unknown, message?: string): asserts value is Uint8ClampedArray {
	if (!isUint8ClampedArray(value)) {
		throw new TypeError(message ?? typeErrorMessage('Uint8ClampedArray', value));
	}
}

export function assertUndefined(value: unknown, message?: string): asserts value is undefined {
	if (!isUndefined(value)) {
		throw new TypeError(message ?? typeErrorMessage('undefined', value));
	}
}

export function assertUrlInstance(value: unknown, message?: string): asserts value is URL {
	if (!isUrlInstance(value)) {
		throw new TypeError(message ?? typeErrorMessage('URL', value));
	}
}

// eslint-disable-next-line unicorn/prevent-abbreviations
export function assertUrlSearchParams(value: unknown, message?: string): asserts value is URLSearchParams {
	if (!isUrlSearchParams(value)) {

View on GitHub ↗ (pinned to 7821031c66)

Solutions

Construct the exact type: `new Uint8ClampedArray(length)` or `new Uint8ClampedArray(buffer)`.
If you have ImageData, pass `imageData.data`, not the ImageData object.
If clamping semantics don't matter to your code, relax the assertion to `assert.uint8Array` or `assert.typedArray`.

Example fix

// before
assert.uint8ClampedArray(imageData);
// after
assert.uint8ClampedArray(imageData.data);

Defensive patterns

Strategy: type-guard

Validate before calling

if (!is.uint8ClampedArray(value)) {
  value = Uint8ClampedArray.from(value);
}

Type guard

if (is.uint8ClampedArray(value)) {
  // value is Uint8ClampedArray here
}

Try / catch

try {
  assert.uint8ClampedArray(value);
} catch (error) {
  if (error instanceof TypeError) { /* handle wrong typed-array class */ }
  throw error;
}

Prevention

Uint8Array and Uint8ClampedArray are different classes — check which one your API (e.g. ImageData.data) actually returns
Guard with is.uint8ClampedArray() before asserting
Convert explicitly with Uint8ClampedArray.from() when interoperating with plain Uint8Array pipelines

When it happens

Trigger: `assert.uint8ClampedArray(value)` with a Uint8Array, Buffer, plain array, or ArrayBuffer. Most commonly hit around canvas ImageData pipelines, since `ImageData.data` is the main real-world source of Uint8ClampedArray.

Common situations: Image-processing code that built pixel data with `new Uint8Array()` instead of `new Uint8ClampedArray()`; passing `imageData` (the object) instead of `imageData.data`.

Related errors

AI-assisted analysis of sindresorhus/is@7821031c66 (2026-07-31). Data as JSON: /data/errors/b4665b39b3273c56.json. Report an issue: GitHub ↗.