Use it for responsive design, renders only the first child that matches query against the current window width.
import {WindowWidthQuery} from 'libreact/lib/WindowWidthQuery';
import {View} from 'libreact/lib/View';
<WindowWidthQuery>
<View maxWidth={300}>
Up to 300px
</View>
<View>
More than 300px
</View>
</WindowWidthQuery>
<WindowWidthQuery>
is simply a shortcut for
<WindowSizeSensor>{({width}) =>
<WidthQuery width={width}>
{/* Your queries here... */}
</WidthQuery>
}</WindowSizeSensor>