FlowiseAI/Flowise · error · Error

${e}

Error message

${e}

What it means

Thrown by CustomFunction_Utilities.init as the catch-all around executeJavaScriptCode, which runs the user-supplied `javascriptFunction` in a sandbox. The user code raised an exception (syntax error, runtime error, reference error, timeout). Note `throw new Error(e)` coerces `e` to a string, losing the original stack trace and any custom error class — a known code smell.

Solutions

1. Run the function standalone in Node with the same inputs to reproduce and debug.
2. Wrap risky sections inside the user function with try/catch and log details.
3. Confirm all variables the function reads are present in the sandbox (input, variables, flow).
4. If the failure is a timeout, optimize or simplify the function.

Example fix

// before (user function throws, library re-wraps losing stack)
// user code
function run(input) { return undefinedVar + 1 }

// after
function run(input) {
  if (typeof someVar === 'undefined') throw new Error('someVar missing in sandbox')
  return someVar + 1
}
// Library-side fix (avoid losing stack): throw e instanceof Error ? e : new Error(String(e))

async function dryRunUserFn(fnSource: string, sandbox: Record<string, unknown>) {
  // surface syntax/runtime errors with full stack before the node runs
  try {
    const fn = new Function(...Object.keys(sandbox), fnSource)
    return await fn(...Object.values(sandbox))
  } catch (e) {
    throw new Error(`Custom function validation failed: ${(e as Error).message}`)
  }
}

const isUserCodeError = (e: unknown): boolean =>
  e instanceof Error && !/JSON|URL|HTTP|Invalid/i.test(e.message)

try {
  return await customFunction.init(nodeData, input, options)
} catch (e) {
  const msg = (e as Error).message
  if (/is not defined|unexpected token|is not a function|cannot read prop/i.test(msg)) {
    throw new Error(`Bug in custom function: ${msg}`)
  }
  throw e
}

When it happens

Trigger: The custom function references an undefined variable, throws explicitly, has a syntax error, hits an infinite loop/timeout, or calls a sandbox API incorrectly.

Common situations: User-authored JS has a typo or references a variable not in the sandbox; the function assumes globals that are restricted; logic bug throws at runtime; copy-paste left a syntax error.

Related errors

• ${e}
• ${e}
• Document object must contain pageContent and metadata
• ${e}
• NodeVM Execution Error

AI-assisted analysis of FlowiseAI/Flowise@abe4a8601a (2026-08-12). Data as JSON: /api/errors/6b94edbe28ccde10. Report an issue: GitHub.

Appendix: source

Thrown at packages/components/nodes/utilities/CustomFunction/CustomFunction.ts:147

        // Add input variables to sandbox
        if (Object.keys(inputVars).length) {
            for (const item in inputVars) {
                additionalSandbox[`$${item}`] = inputVars[item]
            }
        }

        const sandbox = createCodeExecutionSandbox(input, variables, flow, additionalSandbox)

        try {
            const response = await executeJavaScriptCode(javascriptFunction, sandbox)

            if (typeof response === 'string' && !isEndingNode) {
                return handleEscapeCharacters(response, false)
            }
            return response
        } catch (e) {
            throw new Error(e)
        }
    }

    async run(nodeData: INodeData, input: string, options: ICommonObject): Promise<string> {
        return await this.init(nodeData, input, { ...options, isRun: true })
    }
}

module.exports = { nodeClass: CustomFunction_Utilities }

View on GitHub (pinned to abe4a8601a)