首頁猿問如何使用內(nèi)部函數(shù)更改外部變量的值？

如何使用內(nèi)部函數(shù)更改外部變量的值？

JavaScript

紫衣仙女 2023-04-20 16:19:06

在下面的代碼中，當(dāng)我使用函數(shù) calcScore 時(shí)，外部變量 playerScore 和 computerScore 沒有更新？如何使用函數(shù)更新它？據(jù)我了解，可以從內(nèi)部范圍更改外部變量的值，但為什么它在這里不起作用？ <script> function playRound(playerSelection, computerSelection) { playerSelection = playerSelection.toLowerCase(); computerSelection = computerSelection.toLowerCase(); if (playerSelection === computerSelection) { return "draw"; } else if (playerSelection === "rock"){ if (computerSelection === "scissors") return "win"; else if (computerSelection === "paper") return "lose"; } else if (playerSelection === "paper"){ if (computerSelection === "scissors") return "lose"; else if (computerSelection === "rock") return "win"; } else if (playerSelection === "scissors"){ if (computerSelection === "rock") return "lose"; else if (computerSelection === "paper") return "win"; } } function computerSelection() { let selection = ["rock", "paper", "scissors"]; return selection[Math.floor(Math.random() * selection.length)]; } function calcScore(result, playerScore, computerScore) { if (result === "win") { playerScore += 1; console.log("win"); } else if (result === "lose") { computerScore += 1; console.log("lose"); } else if (result === "draw") { playerScore += 1; computerScore += 1; } }

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2 回答

鴻蒙傳說

TA貢獻(xiàn)1865條經(jīng)驗(yàn) 獲得超7個(gè)贊

Javascript 不會通過引用傳遞變量 - 因此您對函數(shù)所做的任何修改playerScore和computerScore內(nèi)部修改calcScore()都只是該函數(shù)的局部修改。

您可以做的是制作playerScore全局computerScore變量。這樣任何修改都將在全局范圍內(nèi)?；蛘?，您可以calcScore()返回修改后的值。

使用全局方法：

let playerScore = 0;

let computerScore = 0;

function playRound(playerSelection, computerSelection) {

playerSelection = playerSelection.toLowerCase();

computerSelection = computerSelection.toLowerCase();

if (playerSelection === computerSelection) {

return "draw";

}

else if (playerSelection === "rock"){

if (computerSelection === "scissors") return "win";

else if (computerSelection === "paper") return "lose";

}

else if (playerSelection === "paper"){

if (computerSelection === "scissors") return "lose";

else if (computerSelection === "rock") return "win";

}

else if (playerSelection === "scissors"){

if (computerSelection === "rock") return "lose";

else if (computerSelection === "paper") return "win";

}

function computerSelection() {

let selection = ["rock", "paper", "scissors"];

return selection[Math.floor(Math.random() * selection.length)];

}

function calcScore(result) {

if (result === "win") {

playerScore += 1;

console.log("win");

}

else if (result === "lose") {

computerScore += 1;

console.log("lose");

}

else if (result === "draw") {

playerScore += 1;

computerScore += 1;

}

function game() {

for (let i = 1; i <= 5; i++) {

let result = playRound(prompt("Select rock, paper, or scissors!"), computerSelection());

calcScore(result);

console.log(`You have ${playerScore} points! Computer has ${computerScore} points!`);

}

playerScore, computerScore = 0, 0;

}

</script>

替代方法：

function playRound(playerSelection, computerSelection) {

playerSelection = playerSelection.toLowerCase();

computerSelection = computerSelection.toLowerCase();

if (playerSelection === computerSelection) {

return "draw";

}

else if (playerSelection === "rock"){

if (computerSelection === "scissors") return "win";

else if (computerSelection === "paper") return "lose";

}

else if (playerSelection === "paper"){

if (computerSelection === "scissors") return "lose";

else if (computerSelection === "rock") return "win";

}

else if (playerSelection === "scissors"){

if (computerSelection === "rock") return "lose";

else if (computerSelection === "paper") return "win";

}

function computerSelection() {

let selection = ["rock", "paper", "scissors"];

return selection[Math.floor(Math.random() * selection.length)];

}

function calcScore(result, playerScore, computerScore) {

if (result === "win") {

playerScore += 1;

console.log("win");

}

else if (result === "lose") {

computerScore += 1;

console.log("lose");

}

else if (result === "draw") {

playerScore += 1;

computerScore += 1;

}

return [playerScore, computerScore];

}

function game() {

let playerScore = 0;

let computerScore = 0;

for (let i = 1; i <= 5; i++) {

let result = playRound(prompt("Select rock, paper, or scissors!"), computerSelection());

let scores = calcScore(result, playerScore, computerScore);

playerScore += scores[0];

computerScore += scores[1];

console.log(`You have ${playerScore} points! Computer has ${computerScore} points!`);

}

playerScore, computerScore = 0, 0;

}

</script>

反對回復(fù) 2023-04-20

撒科打諢

TA貢獻(xiàn)1934條經(jīng)驗(yàn) 獲得超2個(gè)贊

你兩次定義了這兩個(gè)變量，所以現(xiàn)在我很困惑。您是否希望能夠在游戲函數(shù)中重用這些變量而無需重新定義它們？因?yàn)槿绻沁@樣的話，那么它們應(yīng)該是全局變量而不是函數(shù)參數(shù)（您將無法在該函數(shù)之外使用函數(shù)參數(shù)中定義的變量）。

反對回復(fù) 2023-04-20