JavaScript中else if使用问题：console.log未输出对应结果

原始代码 #

// Array for game options (*added the array as requested*)            
const picks = ["Lapis", "Papyrus", "Scalpellus"];

// Computer's new pick            
const compNewChoice = Math.floor(Math.random() * 3);
console.log("Computer chose " + picks[compNewChoice]);

// Player's new pick          
const playerNewChoice = Math.floor(Math.random() * picks.length);
console.log("Player chose " + picks[playerNewChoice]);

if (compNewChoice === picks[0]) {
    if (playerNewChoice === picks[1]) {
        console.log("Computer chose " + picks[0] + " and Player chose " + picks[1] + " Player Wins!");
    } else if (playerNewChoice === picks[2]) {
        console.log("Computer chose " + picks[0] + " and Player chose " + picks[2] + " Computer Wins!");
    } else {
        console.log(" It's a Draw! Computer chose " + picks[0] + " and Player chose " + picks[0]);
    }          
}

问题现象 #

当电脑选择picks[0]且玩家选择picks[2]时，仅输出：

"Computer chose Lapis"
"Player chose Scalpellus"
未输出预期的胜负结果："Computer chose Lapis and Player chose Scalpellus Computer Wins!"

尝试修改后的代码 #

if (compNewChoice === playerNewChoice) {
    console.log("It's a Draw");    
}

if (compNewChoice === picks[0]) {
    if (playerNewChoice === picks[1]) {
        console.log("Computer chose " + picks[0] + " and Player chose " + picks[1] + " Player Wins!");
    } else if (playerNewChoice === picks[2]) {
        console.log("Computer chose " + picks[0] + " and Player chose " + picks[2] + " Computer Wins!");
    }
}

此时平局判断正常，但胜负判断仍然失效。

问题根源与解决方案 #

核心错误是把数组索引和数组元素值混淆：

• compNewChoice和playerNewChoice是随机生成的数字索引（0、1、2），但代码里却拿它们和picks[0]、picks[1]这类字符串元素做比较，两者类型、值均不匹配，导致条件永远无法触发。

修正方法：将条件判断中的元素值替换为对应索引：

const picks = ["Lapis", "Papyrus", "Scalpellus"];

// Computer's new pick            
const compNewChoice = Math.floor(Math.random() * 3);
console.log("Computer chose " + picks[compNewChoice]);

// Player's new pick          
const playerNewChoice = Math.floor(Math.random() * picks.length);
console.log("Player chose " + picks[playerNewChoice]);

// 先判断平局
if (compNewChoice === playerNewChoice) {
    console.log(`It's a Draw! Computer chose ${picks[compNewChoice]} and Player chose ${picks[playerNewChoice]}`);
} 
// 电脑选Lapis（索引0）的胜负判断
else if (compNewChoice === 0) {
    if (playerNewChoice === 1) {
        console.log(`Computer chose ${picks[0]} and Player chose ${picks[1]} Player Wins!`);
    } else if (playerNewChoice === 2) {
        console.log(`Computer chose ${picks[0]} and Player chose ${picks[2]} Computer Wins!`);
    }
}
// 可继续补充电脑选其他选项的判断逻辑

另外，推荐使用模板字符串（` `）拼接内容，比+运算符更清晰易读。

内容的提问来源于stack exchange，提问作者tre3