How to edit an item in a state array?

My suggestion is to get used to use immutable operations, so you don’t modify internal state object.

As pointed in the react docs:

Never mutate this.state directly, as calling setState() afterwards may
replace the mutation you made. Treat this.state as if it were
immutable.

In this case, you can [1] use slice() to get a new copy of the Array, [2] manipulate the copy, and, then, [3] setState with the new Array. It’s a good practice.

Something like that:

const newIds = this.state.ids.slice() //copy the array
newIds[1] = 'B' //execute the manipulations
this.setState({ids: newIds}) //set the new state