why put arrays in state code example

Example 1: react native update state array of objects

let markers = [ ...this.state.markers ];
markers[index] = {...markers[index], key: value};
this.setState({ markers });

Example 2: how to add array data on state react

this.setState({ myArray: [...this.state.myArray, 'new value'] }) //simple value
this.setState({ myArray: [...this.state.myArray, ...[1,2,3] ] }) //another array