AUR0220

Error Message

AUR0220: Map/Set "size" is a readonly property

Description

This error occurs when a binding or assignment tries to write to the size property of a Map or Set. size is readonly in JavaScript and cannot be assigned to.

Example Trigger

<!-- ❌ size is readonly -->
<template>
  <input value.bind="mySet.size">
</template>

Solution

• Bind to size as a read-only value (one-way/from-view), or expose a derived property.

• Mutate the Map/Set via its methods (add, delete, clear) rather than assigning to size.