dispatch logic

output.js

function output(a, b, format = 'text') {
  const dispatchTable = {
    "text": textOutput,
    "html": htmlOutput
  }
  
  if (dispatchTable[format] === undefined) {
    throw new Error(`unknown format ${format}`)
  }
  
  return dispatchTable[format].call(this, a, b)
}