middleware - Algolia

Signature

function middleware({ instantSearchInstance }) {
  return {
    onStateChange({ uiState }) {},
    subscribe() {},
    unsubscribe() {},
  };
}
const search = instantsearch({
  // ...
});
search.use(middleware);

Middleware is a function that returns an object with onStateChange, subscribe, and unsubscribe functions. The middleware function doesn’t perform any actions itself but lets you inject logic into InstantSearch.js, for example, sending events to Google Analytics. To send Algolia click and conversion events, use the insights middleware.

Requirements

InstantSearch.js v4.8.3 or later.

Examples

JavaScript

function middleware({ instantSearchInstance }) {
  return {
    onStateChange({ uiState }) {
      // Do something with `uiState` whenever the state changes.
    },
    subscribe() {
      // Do something when the InstantSearch instance starts.
    },
    unsubscribe() {
      // Do something when the InstantSearch instance is disposed of.
    },
  };
}

// Declare your instantSearch instance normally
const search = instantsearch({
  // ...
});

// Use your middleware function
search.use(middleware);

Options

instantSearchInstance

object

required

You have access to the instance of instantsearch which lets you read values from the instance or call instance methods like addWidgets, setUiState, and refresh.

JavaScript

function middleware({ instantSearchInstance }) {
  return {
    onStateChange({ uiState }) {
      // ...
    },
    subscribe() {
      // ...
    },
    unsubscribe() {
      // ...
    },
  };
}

Hooks

onStateChange

({ uiState }) => void

required

The function is called with uiState whenever the state changes.

JavaScript

function middleware({ instantSearchInstance }) {
  return {
    // ...
    onStateChange({ uiState }) {
      const indexName = "<your-index-name>";
      const { query } = uiState[indexName];
      const title = document.querySelector("<your-selector>");
      title.innerText = query ? `Query: ${query}` : `No query`;
    },
  };
}

This function is called when the InstantSearch instance starts (when search.start() is called). This is where you can add event listeners, subscribe to an API, and run any side effects.

JavaScript

function middleware({ instantSearchInstance }) {
  let subscription;
  let listener;

  return {
    // ...
    subscribe() {
      subscription = someAPI.subscribe();

      listener = (event) => {
        // do something
      };
      document
        .querySelector("<your-selector>")
        .addEventListener("click", listener);
    },
  };
}

unsubscribe

() => void

required

The function is called when the InstantSearch instance is disposed of. You can clean up anything you initiated in the subscribe function.

JavaScript

function middleware({ instantSearchInstance }) {
  let subscription;
  let listener;

  return {
    // ...
    unsubscribe() {
      subscription.unsubscribe();

      document
        .querySelector("<your-selector>")
        .removeEventListener("click", listener);
    },
  };
}

​About this widget

​Requirements

​Examples

​Options

​Hooks

About this widget

Requirements

Examples

Options

Hooks