Please document how to reference a list of items

Please document how to use forwardRef (the preferred way) to retrieve a list or array of items. For example,

const foo = React.forwardRef( (props,ref) => 
  props.superHeros.map( 
    ( hero, index) => <li ref={  ref  } key={ index }>{ hero }</li>
  ) 
)

Perhaps the key question here is, why not do this?

componentDidMount(){
  const foo = this.refs.root.querySelector('.foo')
  ...
}

Suppose there are 50,000 className='foo' elements that are returned by an embedded component. Is this code not portable? Is this code slower than having 50,000 ref created?

Please document this.

Start with the forwardRef example in the issue and compare it with the componentDidMount/querySelector approach. Document how to reference a list or array of items, including the portability and performance questions raised about many elements. Done means the preferred approach and its trade-offs are clearly explained.