Data function

Reports a Vue component data property that is not a function. Suggests wrapping an object literal with a function.

When defining a component, data must be declared as a function that returns the initial data object, because the same definition will be used for creating numerous instances. If a plain object is still used for data, that very object will be shared by reference across all instances created! With a data function, every time a new instance is created we can simply call it to return a fresh copy of the initial data.