React: Updating state when state is an array of objects

Question

I have an array of objects in state:

this.state = {
  items: [
    {id: 1, someattr: \"a string\", anotherattr: \"\"},
    {id: 2, someattr: \"another string         


        

Answer 1

Your update function would look like this

updateItem(id, itemAttributes) {
  var index = this.state.items.findIndex(x=> x.id === id);
  if (index === -1)
    // handle error
  else
    this.setState({
      items: [
         ...this.state.items.slice(0,index),
         Object.assign({}, this.state.items[index], itemAttributes),
         ...this.state.items.slice(index+1)
      ]
    });
}

And you use it like this

this.updateItem(2, {someattr: 'a new value'});

Gross right?

---

You're going to have a big headache in general if you continue to build a complex application in this manner. I would recommend you look into redux or some other Flux implementation that is better suited for solving these problems.

Redux uses a concept of state reducers which each work on a specific slice of the state of your application. That way you don't have to manually dig through your entire state each time you want to affect a deep change.

The creator of Redux, Dan Abramov, has made two video courses available online for free. Dan is an excellent teacher and I felt comfortable with the Redux pattern after spending just one afternoon with it.

• https://egghead.io/courses/getting-started-with-redux
• https://egghead.io/courses/building-react-applications-with-idiomatic-redux