What's the best way to update a nested property deep inside the State object?

```
// constructor --
this.state.someprop = [{quadrangle: {rectangle: {width: * }}, ...}]
...

```

I want to update width of the rectangle object.

```
this.state.quadrangle.rectangle.width = newvalue // isn't working

```

I could make it work like:

```
const {quadrangle} = this.state
quadrangle.rectangle.width = newvalue
this.setState = {
    quadrangle: quadrangle
}

```

But this method doesn't sound the best way for performance/memory