Some error defined

Hello,

I'm getting this error.

[Vue warn]: Error in data(): "TypeError: __WEBPACK_IMPORTED_MODULE_2__data2_json___default.a.slice is not a function"

TypeError: __WEBPACK_IMPORTED_MODULE_2__data2_json___default.a.slice is not a function

[Vue warn]: Property or method "items" 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.

[Vue warn]: Invalid prop: type check failed for prop "items". Expected Array, got Undefined

[Vue warn]: Error in nextTick: "TypeError: Cannot read property 'length' of undefined"

TypeError: Cannot read property 'length' of undefined

I use it without processing anything, the components you provided.
Is something wrong with my environment settings?