rock-paper-scissors.js

const WIN = 1
const LOSE = -1
const TIE = 0
const methods = ['rock', 'paper', 'scissor']

let score = 0

const gameMap = new Map([
    ['rock-paper', LOSE],
    ['rock-scissor', WIN],
    ['rock-rock', TIE],
    ['paper-paper', TIE],
    ['paper-scissor', LOSE],
    ['paper-rock', WIN],
    ['scissor-paper', WIN],
    ['scissor-scissor', TIE],
    ['scissor-rock', LOSE],
])

const randomItem = items => items[Math.random() * items.length | 0]
const getResult = player => {
    const enemy = randomItem(methods)
    return gameMap.get(`${player}-${enemy}`)
}

score += getResult('scissor')