Storing an object in state of a React component?

this.setState({ abc.xyz: 'new value' }); syntax is not allowed.
You have to pass the whole object.

this.setState({abc: {xyz: 'new value'}});

If you have other variables in abc

var abc = this.state.abc;
abc.xyz = 'new value';
this.setState({abc: abc});

You can have ordinary variables, if they don’t rely on this.props and this.state.