Why is the variable not inserted in JSX?

Question

React

An image should be inserted into the src tag, but unknown is inserted

Answer 1

Inside the component:

this.state = {
beerImage: null,
}

componentDidMount() {
promise.then(beer => this.setState({beerImage: beer.image}))
}

Further inside render(): and now beerImage can be passed to src (if beerImage returns the path to the image):
const {beerImage} = this.state;
<img src={beerImage} />