> For the complete documentation index, see [llms.txt](https://docs.fact-finder.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fact-finder.com/webcomponents-overview/web-components-4.x./api/more-features/middleware.md).

# Middleware

Transform FactFinder requests and responses before components receive data.

## Documentation

### Middleware

Starting with version `1.2.13`, FactFinder Web Components supports middleware.

Middleware modules manipulate data exchanged between FactFinder and Web Components. Register modules through Web Components or JavaScript.

**FactFinder Web Components approach**

Place `ff-middleware` directly inside `ff-communication`. It contains all configured modules.

```html
<ff-communication url="..."
                  version="..."
                  api="..."
                  channel="...">
    <ff-middleware></ff-middleware>
</ff-communication>
```

`ff-middleware` must be an immediate child of `ff-communication`. Otherwise, module registration causes an application error.

**JavaScript approach**

Attach an event handler to `ffReady`. Register modules with `use()` in the relevant middleware namespace.

```javascript
window.addEventListener("ffReady", function (event) {
    const factfinder = event.factfinder;
    factfinder.middleware.response.use(module);
});
```

This example registers response middleware. It runs after FactFinder responds and before `ResultDispatcher` notifies its listeners.

**Available modules**

All modules support Web Components and JavaScript registration. When using Web Components, place every module directly inside `ff-middleware`.

**Response**

Response middleware modifies response data. It is available through `factfinder.middleware.response`. Register modules with `factfinder.middleware.response.use()`.

**MultiAttributeParsing**

`MultiAttributeParsing` parses multi-attribute fields into accessible JavaScript objects. FactFinder returns multi-attribute fields as strings:

```
|Size=M|Material=Cotton|Material=Synthetic fibres|Weight~~g=80|Recommended use=Leisure
```

The module converts that value to:

```json
{
    "Size": [
        { "value": "M", "unit": undefined }
    ],
    "Material": [
        { "value": "Cotton", "unit": undefined },
        { "value": "Synthetic fibres", "unit": undefined }
    ],
    "Weight": [
        { "value": "80", "unit": "g" }
    ],
    "Recommended use": [
        { "value": "Leisure", "unit": undefined }
    ]
}
```

Use non-empty Mustache list sections to render parsed fields. Mustache supports spaces in property names.

```html
<ff-record-list>
    <ff-record>
        <img data-image="{{record.ImageName}}"
             data-image-onerror="../img_not_found.gif">

        <div>
            <div>{{record.Title}}</div>
            <div>Price: <strong>{{record.Price}}</strong></div>

            <div>Recommended use:
                {{#record.MultiFilter.Recommended use}}<span>{{value}}</span>{{/record.MultiFilter.Recommended use}}
            </div>
            <div>Material:
                {{#record.MultiFilter.Material}}<span>{{value}}</span>{{/record.MultiFilter.Material}}
            </div>
            <div>Weight:
                {{#record.MultiFilter.Weight}}<span>{{value}} {{unit}}</span>{{/record.MultiFilter.Properties}}
            </div>
        </div>
    </ff-record>
</ff-record-list>
```

Register `MultiAttributeParsing` with Web Components:

```html
<ff-communication>
    <ff-middleware>
        <ff-multi-attribute-parsing
                src-property="MultiFilter"
                store-in-property="MultiFilter"
                keep-original-in-property="OriginalMultiFilter"
                entry-separator="|"
                key-value-separator="="
        ></ff-multi-attribute-parsing>
    </ff-middleware>
</ff-communication>
```

Or register it with JavaScript:

```javascript
window.addEventListener("ffReady", function (event) {
    const factfinder = event.factfinder;
    factfinder.middleware.response.use(factfinder.middleware.response.MultiAttributeParsing({
        srcProperty: "MultiFilter",
        storeInProperty: "MultiFilter",
        keepOriginalInProperty: "OriginalMultiFilter",
        entrySeparator: "|",
        keyValueSeparator: "="
    }));
});
```

See the API reference for all configuration options.

**ProductTeaserCampaignProcessor**

This module inserts teaser feedback text campaigns into `searchResult.records`. It inserts them at their configured positions.

Each teaser produces an `ff-record` with an `is-teaser` attribute. Its inner HTML contains the text configured in FactFinder.

Configure it with Web Components:

```html
<ff-communication>
    <ff-middleware>
        <ff-product-teaser-campaign-processor></ff-product-teaser-campaign-processor>
    </ff-middleware>
</ff-communication>
```

Or configure it with JavaScript:

```javascript
window.addEventListener("ffReady", function (event) {
    const factfinder = event.factfinder;
    factfinder.middleware.response.use(
        factfinder.middleware.response.ProductTeaserCampaignProcessor()
    );
});
```

## API code

### `ff-middleware`

### `ff-multi-attribute-parsing`

**Properties**

<details>

<summary>Properties</summary>

| Name                                             | Description                                           |
| ------------------------------------------------ | ----------------------------------------------------- |
| **src-property** (String, required)              | Multi-attribute field name returned by FactFinder.    |
| **store-in-property** (String, required)         | Property where the parsed object is stored.           |
| **keep-original-in-property** (String, optional) | Property where the original unparsed value is stored. |
| **entry-separator** (String, default: `"ǀ"`)     | Character separating key-value pairs in FactFinder.   |
| **key-value-separator** (String, default: `"="`) | Character separating each key from its value.         |

</details>

### `ff-product-teaser-campaign-processor`

This element has no properties.


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