appsmithorg/appsmith · error · Error

eventName should be a string

Error message

eventName should be a string

What it means

Thrown by window.appsmith.triggerEvent() in the WDS Custom Widget iframe. eventName must be a string because it becomes the event key in the CUSTOM_WIDGET_TRIGGER_EVENT payload sent to the parent app. The WDS variant uses the same triggerEvent contract as the legacy widget.

Source

Thrown at app/client/src/widgets/wds/WDSCustomWidget/component/customWidgetscript.js:252

            }
          };
        },
        updateModel: (obj) => {
          if (!obj || typeof obj !== "object") {
            throw new Error("updateModel expects an object as parameter");
          }

          appsmith.model = Object.assign(
            Object.assign({}, appsmith.model),
            obj,
          );

          // Send an update model message to the parent
          channel.postMessage(EVENTS.CUSTOM_WIDGET_UPDATE_MODEL, obj);
        },
        triggerEvent: (eventName, contextObj) => {
          if (typeof eventName !== "string") {
            throw new Error("eventName should be a string");
          } else if (contextObj && typeof contextObj !== "object") {
            throw new Error("contextObj should be an object");
          }

          // Send a trigger event message to the parent
          channel.postMessage(EVENTS.CUSTOM_WIDGET_TRIGGER_EVENT, {
            eventName,
            contextObj,
          });
        },
        model: {},
        onReady: (fn) => {
          if (typeof fn !== "function") {
            throw new Error("onReady expects a function as parameter");
          }

          onReady = fn;

View on GitHub (pinned to 8cd9021c24)

Solutions

1. Pass a string literal event name: appsmith.triggerEvent('onRowSelect').
2. Coerce known-safe identifiers: appsmith.triggerEvent(String(e.type)).
3. Centralize event names in a const map and reference only those.
4. Ensure a matching event handler is bound on the WDS Custom Widget in the Appsmith app.

Example fix

// before
appsmith.triggerEvent(event); // event is an object

// after
appsmith.triggerEvent(event.name, event.detail);

if (typeof eventName !== 'string' || eventName.length === 0) {
  throw new TypeError('triggerEvent eventName must be a non-empty string');
}
appsmith.triggerEvent(eventName, detail);

const isEventName = (v) => typeof v === 'string' && v.trim().length > 0;

// usage
if (isEventName(name)) appsmith.triggerEvent(name, detail);

try {
  appsmith.triggerEvent(String(name), detail);
} catch (e) {
  console.error('triggerEvent rejected name:', e.message);
}

When it happens

Trigger: Calling appsmith.triggerEvent(undefined), appsmith.triggerEvent(123), appsmith.triggerEvent({type:'select'}), or appsmith.triggerEvent() with no first argument in the WDS widget.

Common situations: Forwarding a numeric event code; passing an event object instead of its string type field; referencing an event-name constant that was not exported from the shared module.

Related errors

• onThemeChange expects a function as parameter
• onModelChange expects a function as parameter
• updateModel expects an object as parameter
• contextObj should be an object
• onReady expects a function as parameter

AI-assisted analysis of appsmithorg/appsmith@8cd9021c24 (2026-08-12). Data as JSON: /api/errors/81f55c9d1b71b5f1. Report an issue: GitHub.