n8n-io/n8n · error · ExpressionExtensionError

keys and values not of equal length

Error message

keys and values not of equal length

What it means

`zip` also requires the two arrays to have EQUAL length (`keys.length !== values.length`); otherwise the resulting object would have undefined values for the missing positions.

Source

Thrown at packages/@n8n/expression-runtime/src/extensions/function-extensions.ts:28

	let curr = start;
	for (let i = 0; i < size; i++) {
		if (start < end) {
			arr[i] = curr++;
		} else {
			arr[i] = curr--;
		}
	}

	return arr;
};

const zip = (keys: unknown[], values: unknown[]): unknown => {
	if (!Array.isArray(keys) || !Array.isArray(values)) {
		throw new ExpressionExtensionError('keys and values must be arrays');
	}
	if (keys.length !== values.length) {
		throw new ExpressionExtensionError('keys and values not of equal length');
	}
	const result: Record<string, unknown> = {};
	for (let i = 0; i < keys.length; i++) {
		result[keys[i] as string] = values[i];
	}
	return result;
};

const average = (...args: number[]) => {
	return aAverage(args);
};

const not = (value: unknown): boolean => {
	return !value;
};

function ifEmpty<T, V>(value: V, defaultValue: T) {
	if (arguments.length !== 2) {

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Pad the shorter array (e.g. fill with `null`) or truncate the longer one to equal length.
2. Validate `keys.length === values.length` upstream in a Code node.
3. Re-emit the upstream data so both lists are guaranteed parallel.

Example fix

// before
{{ zip(['a','b','c'], [1,2]) }}
// after
{{ zip(['a','b','c'], [1,2,null]) }}

const { keys, values } = $json;
if (keys.length !== values.length) {
  throw new Error(`zip(): length mismatch (${keys.length} vs ${values.length})`);
}
return $json;

const sameLength = (a: unknown[], b: unknown[]): boolean => a.length === b.length;

When it happens

Trigger: A header array with 5 entries zipped against a row array with 4; mismatched parallel lists from upstream.

Common situations: Ragged source data (CSV rows with fewer columns than the header); one source pruned entries the other kept.

Related errors

• intersection(): expected array arg, e.g. .intersection([1, 2
• keys and values must be arrays
• Filter operator "${operator}" on key "${key}" requires a non
• Filter operator "${operator}" on key "${key}" requires array
• Unsupported unit '${String(errorUnit)}'. Supported: ${durati

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/1a9c3f1b8bce4071. Report an issue: GitHub.