Uncaught TypeError: Cannot read property 'extend' of undefined' - cq.extend

When we try to create a custom widget we extend the widget from the CompositeField. When we render this custom widget script, we may get error like "Uncaught TypeError: Cannot read property 'extend' of undefined' ".

Solution:When custom component adds a dependency on cq.widgets it will always fail in the publisher.

When we include below statement in clientlibs, this script is also evaluated in the publisher for the purpose of assigning the variable, even if it is never used.

Search.CustomWidget = CQ.Ext.extend(CQ.form.CompositeField, {
You can make this work by having the authoring part completely separated from the rest of the component so that the publisher never tries to execute any part of it. For example by using a different category which is only included using WCMMode.fromRequest(request) != WCMMode.DISABLED