[Vue Warn] Property or method "currentIndex" is not defined - How to fix

"[Vue warn]: Property or method "currentIndex" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property. See: https://vuejs.org/v2/guide/reactivity.html#Declaring-Reactive-Properties.\n\nfound in\n\n---> \n\nWhat is this error and how to fix it? This error occurs when you reference a property or method named "currentIndex" in your Vue template, but it's not defined. To solve this, follow these steps:\n\n1. Check your template: Make sure you are not referencing "currentIndex" in your template, or confirm you have defined it correctly.\n\n2. Check your data: If you intend to use "currentIndex" in your template, ensure you've declared it in your Vue instance's "data" option. Example:\n\njavascript\ndata() {\n return {\n currentIndex: 0\n }\n}\n\n\n3. Check computed properties or methods: If "currentIndex" is a computed property or method, not a direct data property, make sure it's correctly defined and declared. Example:\n\njavascript\ncomputed: {\n currentIndex() {\n return // Calculation logic\n }\n}\n\n\n4. Check component scope: If you use "currentIndex" within a component, ensure it's correctly defined and declared within that component's scope. If it's a prop passed from a parent component, declare it as a receivable property using the "props" option.\n\nAfter following these steps, the error should disappear. If the problem persists, there might be other issues in your code, so continue checking potential causes.