使用ghcjs-dom過濾[Node]到[Element]

Question

我正在使用ghcjs-dom。我如何過濾節點數組中的元素？

import GHCJS.DOM.Types 

nodesToElements :: [Node] -> [Element] 
nodesToElements = ?? 

或

nodesToElements :: [Node] -> IO [Element] 
nodesToElements = ?? 

Answer 1

import GHCJS.DOM.Types 
import Data.Maybe (mapMaybe) 

nodeToElement :: Node -> Maybe Element 
nodeToElement node = if node `isA` gTypeElement 
        then Just $ castToElement node 
        else Nothing 

nodesToElements :: [Node] -> [Element] 
nodesToElements = mapMaybe nodeToElement