eventmap.js

main()
function main(){
  console.log('main')
  let listener = EventMap(mapperUpperCase)(window)
  
  listener.addEventListener('keydown', e=>console.info('down', e))
  listener.addEventListener('keyup', e=>console.info('up', e))
  
}


//passthrough
function mapperUpperCase(handler){
  return function callMapper(action, event){
    let key = event.key
    if(key.length == 1)
      key = key.toUpperCase()
    console.log(`mapper ${action}`, event)
    handler[action]({key})
  }
}


function EventMap(mapper){
  let handler = {}
  return function(listener){
    let callMapper = mapper(handler)
    
    init()
    return {addEventListener}
  
    function init(){
      console.info('init EventMap')
    }

    function addEventListener(name, callback){
      if(!handler.hasOwnProperty(name)){
        listener.addEventListener(name,(e)=>{
          callMapper(name, e)})
      } 
      handler[name] = callback
    }
  }
}