numpad decode

numpad.js

let keymap = [
  "",
  "ABC",
  "DEF",
  "GHI",
  "JKL",
  "MNO",
  "PQRS",
  "TUV",
  "WXYZ"
]
.map((item, i)=>{
  return {
    [i+1]: item.split("").map(
      (letter, i)=>{return {[i+1]: letter}}
    ).reduce((a, b)=>{
      return Object.assign({}, a, b)
    }, {})
  }
})
.reduce((a, b)=>{
  return Object.assign({}, a, b)
}, {})

let input = process.argv.slice(2)

let result = input.map((code)=>{
  [i, j] = code.split("")
  return keymap[i][j]
}).join("")

console.log(result)