Find and replace key from array in react native

I am trying to implement checked and unchecked box in a flatlist.

I have taken a keyword checked. On the basis of this keyword I want to show the checkbox (checked or unchecked)

I am trying to update the checked key on selection and deselection.

But getting errors.

Can anyone tell me what is wrong here?

Here is my code:

updateItem(item) {
    this.setState({
      array :  ! this.array.findIndex(item => item.title === item.title).checked
    })
    this.setState({ array: [...this.array] });

}

My array is:

(this.array = [{title: "Option 1",checked:"false"},
      { title: "Option 2" ,checked:"false"},
      { title: "Option 3",checked:"false"},
      { title: "Option 4",checked:"false" },
      { title: "Option 5",checked:"false"}
    ])

Thanks!