grafana/k6 · error

got error while trying to check if argument is ArrayBufferVi

Error message

got error while trying to check if argument is ArrayBufferView: %w

What it means

Wrap of a Sobek runtime failure in send()'s default branch: before deciding whether the argument is an ArrayBufferView, k6 invokes the script's ArrayBuffer.isView function inside rt.Try. The wrapped error means that lookup/call itself threw — the ArrayBuffer global or its isView method was replaced or shadowed by script code — not that the argument type is wrong.

Source

Thrown at internal/js/modules/k6/websockets/websockets.go:681

		rt := w.vu.Runtime()
		obj := msg.ToObject(rt)
		if !isBlob(obj, w.blobConstructor) {
			common.Throw(rt, fmt.Errorf("unsupported send type %T", o))
		}

		b := extractBytes(obj, rt)
		w.bufferedAmount += len(b)
		w.writeQueueCh <- message{
			mtype: websocket.BinaryMessage,
			data:  b,
			t:     time.Now(),
		}
	default:
		rt := w.vu.Runtime()
		isView, err := isArrayBufferView(rt, msg)
		if err != nil {
			common.Throw(rt,
				fmt.Errorf("got error while trying to check if argument is ArrayBufferView: %w", err))
		}
		if !isView {
			common.Throw(rt, fmt.Errorf("unsupported send type %T", o))
		}

		var b []byte
		err = rt.ExportTo(msg, &b)
		if err != nil {
			common.Throw(rt,
				fmt.Errorf("got error while trying to export ArrayBufferView to bytes: %w", err))
		}
		w.bufferedAmount += len(b)
		w.writeQueueCh <- message{
			mtype: websocket.BinaryMessage,
			data:  b,
			t:     time.Now(),
		}
	}

View on GitHub (pinned to 165bb3c1a4)

Solutions

1. Do not override, delete, or shadow the global ArrayBuffer object in the script
2. Check for script-side polyfills or mocks that replace built-in constructors
3. Send data as a plain string or Blob to bypass the ArrayBufferView check

When it happens

Trigger: Thrown at internal/js/modules/k6/websockets/websockets.go:656 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@165bb3c1a4 (2026-08-18). Data as JSON: /api/errors/6667a6f6a5184c78. Report an issue: GitHub.