Embed Javascript Events API

Looker Embed JavaScript Events

This skill enables agents to assist users in implementing and troubleshooting interactive communication between a host application and an embedded Looker iframe using JavaScript events.

Overview

Looker embedding uses the HTML5 postMessage API to pass messages between the host page and the Looker iframe. This allows for:

• Event Monitoring: Detecting when a dashboard starts/finishes running, when filters change, or when a user navigates.
• Bi-directional Control: Sending commands (actions) from the host app into Looker to trigger runs, update filters, or change layouts.

1. Listening for Events

The host application must listen for message events on the window object.

Implementation Pattern

window.addEventListener("message", function (event) {
  // 1. ALWAYS verify the origin for security
  if (event.origin !== "https://your_company.looker.com") return;

  // 2. Verify the source is the Looker iframe
  const lookerIframe = document.getElementById("looker-embed");
  if (event.source !== lookerIframe.contentWindow) return;

  // 3. Parse and handle the event
  const data = typeof event.data === 'string' ? JSON.parse(event.data) : event.data;
  console.log("Looker Event:", data.type, data);
});

2. Event Type Reference

Dashboard Events

• dashboard:loaded: Fired when the dashboard metadata is loaded (before queries run).
• dashboard:run:start: Fired when tiles begin querying for data.
• dashboard:run:complete: Fired when all tiles have finished loading. Includes dashboard.options (layout/elements).
• dashboard:filters:update: Fired when a user changes filters within the dashboard.
• dashboard:tile:view: Fired when a user clicks "View Original Look" on a tile. Cancellable.
• dashboard:tile:merge: Fired when a user clicks "Edit Merged Query". Cancellable.

Look & Explore Events

• look:ready: Fired when a Look begins to load.
• look:run:start / look:run:complete: Lifecycle of a Look query.
• explore:run:start / explore:run:complete: Lifecycle of an Explore query.
• explore:state:changed: Fired when the Explore URL/state changes (e.g., field selection).

Page & System Events

• page:changed: Fired when navigating between content types (e.g., from Dashboard to Look).
• page:properties:changed: Fired when the iframe height changes (Dashboards only).
• session:expired: Fired when the user's session ends.
• env:client:dialog: Fired when a Looker dialog (like a drill) is opened.

3. Sending Actions to Looker

Actions are sent from the host app to Looker using postMessage.

Implementation Pattern

const sendLookerAction = (action) => {
  const iframe = document.getElementById("looker-embed");
  iframe.contentWindow.postMessage(JSON.stringify(action), "https://your_company.looker.com");
};

// Example: Triggering a dashboard run
sendLookerAction({ type: "dashboard:run" });

// Example: Updating filters
sendLookerAction({
  type: "dashboard:filters:update",
  filters: { "State": "California", "Date": "Last 7 Days" }
});

Common Actions

• dashboard:run / look:run / explore:run: Force a refresh of the content.
• dashboard:load: Load a different dashboard ID in the same iframe.
• dashboard:options:set: Programmatically change tile visibility or layout.
• env:host:scroll: Pass the host's scroll position to Looker for proper dialog positioning.

4. Using the Embed SDK (Recommended)

While manual postMessage handling works, the Looker Embed SDK abstracts this complexity and provides a more idiomatic interface.

Initializing a Connection

import { LookerEmbedSDK } from '@looker/embed-sdk';

LookerEmbedSDK.createDashboardWithId(123)
  .appendTo('#container')
  .on('dashboard:run:complete', (e) => console.log('Finished!', e))
  .build()
  .connect()
  .then((dashboard) => {
    // 'dashboard' implements ILookerConnection
    // Trigger a run
    dashboard.send('dashboard:run');
  })
  .catch(console.error);

Sending Actions via ILookerConnection.send

The send method is a low-level way to trigger actions within the Looker iframe. It is available on all connection types (Dashboards, Explores, Looks).

• Signature: send(message: string, params?: any): void
• When to use: Use send to dispatch any supported message to the Looker host when a high-level helper method isn't available.

// Example: Updating filters
dashboard.send('dashboard:filters:update', {
  filters: { 'State': 'California' }
});

// Example: Force a run
dashboard.send('dashboard:run');

Receiving Data via sendAndReceive

If you need a response back from the embedded content, use sendAndReceive.

• Signature: sendAndReceive(message: string, params?: any): Promise<any>

dashboard.sendAndReceive('dashboard:options')
  .then((options) => console.log('Dashboard Options:', options));

5. Troubleshooting & Best Practices

• Origin Security: Always check event.origin to prevent Cross-Site Scripting (XSS).
• JSON Parsing: Older Looker versions might send stringified JSON, while newer ones might send objects. Use a robust parser.
• Cancellable Events: Events like dashboard:tile:view can be cancelled by returning { cancel: true } in some SDK implementations to override default behavior.
• Race Conditions: Ensure the iframe has sent page:changed or a similar "ready" event before sending the first action.