javascript - How to update nested state properties in React

Question

I'm trying to organize my state by using nested property like this:

this.state = {
   someProperty: {
      flag:true
   }
}

But updating state like this,

this.setState({ someProperty.flag: false });

doesn't work. How can this be done correctly?

Answer 1

In order to setState for a nested object you can follow the below approach as I think setState doesn't handle nested updates.

var someProperty = {...this.state.someProperty}
someProperty.flag = true;
this.setState({someProperty})

The idea is to create a dummy object perform operations on it and then replace the component's state with the updated object

Now, the spread operator creates only one level nested copy of the object. If your state is highly nested like:

this.state = {
   someProperty: {
      someOtherProperty: {
          anotherProperty: {
             flag: true
          }
          ..
      }
      ...
   }
   ...
}

You could setState using spread operator at each level like

this.setState(prevState => ({
    ...prevState,
    someProperty: {
        ...prevState.someProperty,
        someOtherProperty: {
            ...prevState.someProperty.someOtherProperty, 
            anotherProperty: {
               ...prevState.someProperty.someOtherProperty.anotherProperty,
               flag: false
            }
        }
    }
}))

However the above syntax get every ugly as the state becomes more and more nested and hence I recommend you to use immutability-helper package to update the state.

See this answer on how to update state with immutability-helper.