> For the complete documentation index, see [llms.txt](https://docs.aurelia.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aurelia.io/developer-guides/error-messages/ui-virtualization/aur6005.md).

# AUR6005

## Error Message

`AUR6005: Unable to find a strategy for collection type: {{type}}. Supported types: Array, null/undefined.`

Where `{{type}}` is the runtime type name/description of the provided collection.

## Description

This error occurs when `virtual-repeat` is given a collection type it doesn’t know how to virtualize.

## Example Trigger

```ts
export class MyList {
  // ❌ Map is not supported by the default strategy set
  items = new Map<string, unknown>();
}
```

```html
<template>
  <div virtual-repeat.for="item of items">${item}</div>
</template>
```

## Correct Usage

* Use an `Array` as the source for `virtual-repeat` (convert other structures to an array).

```ts
export class MyList {
  private readonly map = new Map<string, unknown>();

  get items() {
    return [...this.map.values()];
  }
}
```

## Troubleshooting

* Log the value you bind to `virtual-repeat.for` and verify it is an `Array`.
* If you need to virtualize a custom collection type, look for (or implement) a supported collection strategy for that type.


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