[Vuejs]-How do I overwrite input items in session in Vue.js?

That console message is generated whenever a new property is added to the object returned from data. You shouldn’t be getting that message for properties like “category” or “url”, but you will if something else is added.

Try generating console messages wherever $set is called to ensure that key or data[0] is not a new unknown property. If it is, try adding it to the data object as a null or empty string.