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Debugged: "Attempted to assign to readonly property." iOS 8 TypeError

By Todd H Gardner

A webkit bug that shipped in iOS 8 beta 5 and appears to have been partially included in the launch of iOS 8 and 8.1 is affecting many of our customers. It does not seem to impact all iOS8 uniformly; different versions of webkit seem to be involved.

The error will be recorded as:

TypeError: Attempted to assign to readonly property.

The issue is reported in WebKit as WebIDL attributes should be implemented as getters and setters on the prototype object and involves the rendering of elements into the DOM. This bug is known to impact:


Each framework is encountering this problem in a unique way. Check on the bug report for your platform for a fix. In some cases, upgrading to the latest version solves the issue. In others, you may be able to work around the issue by removing the “use strict” declaration from your code.

Todd H Gardner
Todd H Gardner
CEO and Cofounder