Question

我在尝试编译它的代码时遇到问题，但它使我无法将也许元素与元素

为什么？可能如何工作？如何将其转换为值？为什么这么难理解单子和函子，为什么没有一个简单的库来让一些新手开始使用purescript？：P

（对于那些听不懂的人，我只是问前三个）

module Main where

import Prelude --(Unit, bind, pure,  ($), (<$>))
import Effect (Effect)
import Data.Maybe --(Just,Maybe,fromJust, fromMaybe)
import Data.Foldable (traverse_)
import Effect.Console (log)

import Web.HTML (window)
import Web.HTML.Window (document)
import Web.HTML.HTMLDocument (toNonElementParentNode)
import Web.Event.Event (Event, target)
import Web.HTML.HTMLInputElement (value, fromEventTarget)

import Web.DOM.NonElementParentNode (NonElementParentNode,getElementById)
import Web.DOM.Node (setTextContent)
import Web.DOM.Element (Element,toNode)
import Web.Event.EventTarget (addEventListener)

pname = "#inputName" :: String
bname = "#badgeName" :: String

main :: Effect Unit
main = do
  nod1 <- returnNonElementParentNode
--querySelector :: QuerySelector -> ParentNode -> Effect (Maybe Element)
  elementTarget <- getElementById pname nod1
--addEventListener :: EventType -> EventListener -> Boolean -> EventTarget
  addEventListener "input" updateBadge false elementTarget

updateBadge :: Event -> Unit
updateBadge event = do
  nod2 <- returnNonElementParentNode
  elementTarget <- getElementById bname nod2

  tget <- target event
  inml <- fromEventTarget tget
  input <- value inml

  badge <- toNode (pure elementTarget)

  if not(badge == Nothing) 
    then setTextContent input (toNode badge) 
    else Nothing

returnNonElementParentNode :: Effect NonElementParentNode
returnNonElementParentNode = do 
  win <- window
  doc <- document win
  --let nd  = toNonElementParentNode doc
  let 
      nod = toNonElementParentNode doc
  pure nod

我只想了解如何从htmlInputElement获取输入值并将其传递给另一个HTMLElement的textContent

如何将也许转换为值以传递给 toNode 函数

Answer 1

模式匹配... https://github.com/purescript/documentation/blob/master/language/Pattern-Matching.md
Data.Maybe＃v：maybe ... https://pursuit.purescript.org/packages/purescript-maybe/4.0.1/docs/Data.Maybe#v:maybe
Data.Maybe＃v：fromMaybe ... https://pursuit.purescript.org/packages/purescript-maybe/4.0.1/docs/Data.Maybe#v:fromMaybe
Partial.Unsafe＃v：unsafePartial + Data.Maybe＃v：from https://pursuit.purescript.org/packages/purescript-partial/2.0.1/docs/Partial.Unsafe#v:unsafePartial https://pursuit.purescript.org/packages/purescript-maybe/4.0.1/docs/Data.Maybe#v:fromJust

如何获得将Maybe转化为价值的方法？

1 个答案: