為什么我的函式即使我定義了它也會回傳未定義？

這是來自 The Odin Project 的 Rock, Paper, Scissors 任務。當我運行代碼時， playerSelection 和 computerSelection 變數是未定義的。即使我定義了這些變數，為什么它顯示未定義？

let playerScore = 0;
let computerScore = 0;
let playerSelection = 'scissors';

const choices = ['rock', 'paper', 'scissors'];

function computerPlay() {
    let computerResult = [Math.floor(Math.random() * choices.length)];
    return computerSelection = choices[computerResult];
}

console.log(`Player Score: ${playerScore}`);
console.log(`Computer Score: ${computerScore}`);
console.log(`Computer picked ${computerPlay()}`);


function playRound(playerSelection, computerSelection) {
    if (computerSelection === playerSelection) {
        console.log(`${playerSelection} vs. ${computerSelection}. It's a tie!`);
    }
    else if (computerSelection === 'rock' && playerSelection === 'scissors'){
        console.log(`${playerSelection} vs. ${computerSelection}. You lose! Try again next time.`);
        computerScore  ;
    }
    else if (computerSelection === 'paper' && playerSelection === 'rock'){
        console.log(`${playerSelection} vs. ${computerSelection}. You lose! Try again next time.`);
        computerScore  ;
    }
    else if (computerSelection === 'scissors' && playerSelection === 'paper'){
        console.log(`${playerSelection} vs. ${computerSelection}. You lose! Try again next time.`);
        computerScore  ;
    }
    else if (playerScore === 'rock' && computerSelection === 'scissors'){
        console.log(`${playerSelection} vs. ${computerSelection}. You win!`);
        playerScore  ;
    }
    else if (playerScore === 'paper' && computerSelection === 'rock'){
        console.log(`${playerSelection} vs. ${computerSelection}. You win!`);
        playerScore  ;
    }
    else (playerScore === 'scissors' && computerSelection === 'paper') 
        console.log(`${playerSelection} vs. ${computerSelection}. You win!`);
        playerScore  ;
    }

playRound();

uj5u.com熱心網友回復：

您依賴此呼叫computerPlayer

console.log(`Computer picked ${computerPlay()}`);

computerSelection在此處創建全域變數

return computerSelection = choices[computerResult];

然后，通過將引數定義為具有相同識別符號，您可以在 范圍內隱藏這些全域變數。playRound

function playRound(playerSelection, computerSelection) {

快速而混亂的解決方法是呼叫playRound，從外部范圍傳入變數

playRound(playerSelection, computerSelection)

playRound有不平衡的花括號，以及像playerScore === 'rock'andelse而不是else if.

這些行正在創建一個陣列，其中包含[0, 2]范圍內的單個數字。

let computerResult = [Math.floor(Math.random() * choices.length)];
return computerSelection = choices[computerResult];

并將此陣列用作另一個陣列的索引。由于型別強制，這幾乎不起作用。

考慮進行一些重構，以重構此代碼以減少對生成和在陌生地方使用全域變數的依賴。

您也不需要詳盡地檢查每種可能性組合。如果您檢查了玩家未獲勝的所有結果，那么剩下的就是玩家確實獲勝的結果。

一個例子：

const rps = [ 'rock', 'paper', 'scissors' ];

let playerScore = 0;
let computerScore = 0;

const pickRandom = arr => arr[Math.floor(Math.random() * arr.length)];

const playRound = (playerSelection, computerSelection) => {
    if (computerSelection === playerSelection) {
        console.log(`${playerSelection} vs. ${computerSelection}. It's a tie!`);
    } else if (
        (computerSelection === 'rock' && playerSelection === 'scissors') ||
        (computerSelection === 'paper' && playerSelection === 'rock') ||
        (computerSelection === 'scissors' && playerSelection === 'paper')
    ) {
        console.log(`${playerSelection} vs. ${computerSelection}. You lose! Try again next time.`);
        computerScore  ;
    } else {
        console.log(`${playerSelection} vs. ${computerSelection}. You win!`);
        playerScore  ;
    }
};

let rounds = 3;

while (rounds--) {
    let playerChoice = 'scissors'; // make this interactive!
    let computerChoice = pickRandom(rps);

    console.log(`Player picked: ${playerChoice}`);
    console.log(`Computer picked ${computerChoice}`);

    playRound(playerChoice, computerChoice);

    console.log(`Player Score: ${playerScore}`);
    console.log(`Computer Score: ${computerScore}`);
}

不過，可能希望快速轉向面向物件的方法，以解開更多全域變數，并將游戲狀態包含在單個物件中。

uj5u.com熱心網友回復：

您忘記將引數傳遞給您的函式。

playRound(compuplayerSelection, computerSelection);

此外，您在獲勝宣告中寫了 playerScore 而不是 playerSelection，并且您忘記將“if”放在最后一個。

let playerScore = 0;
let computerScore = 0;
let playerSelection = 'scissors';

const choices = ['rock', 'paper', 'scissors'];

function computerPlay() {
    let computerResult = [Math.floor(Math.random() * choices.length)];
    return computerSelection = choices[computerResult];
}

console.log(`Player Score: ${playerScore}`);
console.log(`Computer Score: ${computerScore}`);
console.log(`Computer picked ${computerPlay()}`);


function playRound(playerSelection, computerSelection) {
    if (computerSelection === playerSelection) {
        console.log(`${playerSelection} vs. ${computerSelection}. It's a tie!`);
    }
    else if (computerSelection === 'rock' && playerSelection === 'scissors'){
        console.log(`${playerSelection} vs. ${computerSelection}. You lose! Try again next time.`);
        computerScore  ;
    }
    else if (computerSelection === 'paper' && playerSelection === 'rock'){
        console.log(`${playerSelection} vs. ${computerSelection}. You lose! Try again next time.`);
        computerScore  ;
    }
    else if (computerSelection === 'scissors' && playerSelection === 'paper'){
        console.log(`${playerSelection} vs. ${computerSelection}. You lose! Try again next time.`);
        computerScore  ;
    }
    else if (playerSelection === 'rock' && computerSelection === 'scissors'){
        console.log(`${playerSelection} vs. ${computerSelection}. You win!`);
        playerScore  ;
    }
    else if (playerSelection === 'paper' && computerSelection === 'rock'){
        console.log(`${playerSelection} vs. ${computerSelection}. You win!`);
        playerScore  ;
    }
    else if (playerSelection === 'scissors' && computerSelection === 'paper') 
        console.log(`${playerSelection} vs. ${computerSelection}. You win!`);
        playerScore  ;
    }

playRound(playerSelection, computerSelection);

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