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UI libraries / Vue InstantSearch / Widgets

middleware

Signature 
<ais-instant-search
  index-name="instant_search"
  :search-client="searchClient"
  :middlewares="middlewares"
>
  <!-- Widgets -->
</ais-instant-search>
See code examples

About this widget

The middleware function returns an object with onStateChange, subscribe, and unsubscribe functions.

The middleware function doesn’t perform any actions itself but allows you to inject functionality into Vue InstantSearch:

Requirements

Vue InstantSearch v3.7.0 or later.

Examples

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<template>
  <ais-instant-search
    index-name="instant_search"
    :search-client="searchClient"
    :middlewares="middlewares"
  >
    <!-- Widgets -->
  </ais-instant-search>
</template>

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

  export default {
    data() {
      return {
        // ...
        middlewares: [middleware]
      }
    }
  }
</script>

Options

Parameter Description
instantSearchInstance
type: 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.
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function middleware({ instantSearchInstance }) {
  return {
    onStateChange({ uiState }) {
      // ...
    },
    subscribe() {
      // ...
    },
    unsubscribe() {
      // ...
    }
  }
}

Hooks

Parameter Description
onStateChange
type: ({ uiState }) => void
Required

This function is called with uiState whenever the state changes.
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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`;
    },
  }
}
subscribe
type: () => void
Required

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

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

      listener = (event) => {
        // do something
      }
      document.querySelector('<your-selector>').addEventListener('click', listener);
    },
  }
}
unsubscribe
type: () => void
Required

This function is called when the InstantSearch instance is disposed of. You can clean up anything you initiated in the subscribe function.
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function middleware({ instantSearchInstance }) {
  let subscription;
  let listener;

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

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