AUR0210

Error Message

AUR0210: Unrecognised collection type {{type}}.

Where {{type}} is the runtime type description of the value Aurelia tried to treat as a collection.

Description

This error occurs when Aurelia’s collection observation logic receives a value that it does not recognize as a supported collection type (for example not an Array, Map, Set, or another supported type in the given context).

Common Scenarios

<!-- ❌ items is an unexpected type -->
<template>
  <div repeat.for="item of items">${item}</div>
</template>

export class MyVm {
  // e.g. accidentally assigned an object instead of an array
  items: unknown = { a: 1 };
}

Solutions

• Ensure the bound value is a supported collection type for the feature you’re using (most commonly an Array).

• Initialize collections to an empty array ([]) instead of null/undefined when appropriate.

Troubleshooting

• Log the value being iterated/observed and confirm its type.

• Track where the value is assigned to locate the incorrect assignment.