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javascript - 承诺：过早地解决返回值

问题描述

更新：我的问题的根源是，我通过他们的 uuid 为我的数组分配值。所以即测验[uuid] = x。因此，数组长度为 0，并且该属性显然未在 json 响应中处理。

我正在构建一个函数，在其中初始化对象测验并在 for 循环中更改它。完成后，我想兑现承诺。当我调用这个函数时，我只收到初始化值并且缺少来自 for 循环的更改。console.log(quiz) 记录对象的变化。我找不到我的错误...

我尝试了一些 if 子句，只在 for 循环完成时调用 resolve 函数。这导致相同的结果或没有响应。

app.get('/playQuiz', function (req, res) {
    playQuiz().then(data => {
        res.status(200).json({
            quiz: data
        });
    });    
});

async function playQuiz(){
    var players = {
        puuids: [],
        stats: []
    }
    credentials = await getCredentials();

    token = credentials.token;
    port = credentials.port;

    players.puuids = await getLobby(port, token);
    for(i=0; i<players.puuids.length; i++){
        players.stats[i] = await getStats(port, token, players.puuids[i])
    }

    let quiz = await evaluateQuiz(players)
    console.log(quiz); // This displays the object quiz with the changes from the loop
    return quiz; //The response i get displayed in Postman from this line, does not show the changes in i.e. csScore. It only shows an empty array.
}

function evaluateQuiz(players){
    return new Promise((resolve, reject) => {
        var quiz = [{
                questionId: 1,
                question: "Who has the most cs per game?",
                csScore: []
            },
            {
                questionId: 2,
                question: "Who has the highest vision score per game?",
                vsScore: []
            },
            {
                questionId: 3,
                question: "Who has the best win rate?",
                winRate: []
            },
            {
                questionId: 4,
                question: "Who has the most quadra kills?",
                quadraKills: []
            },
            {
                questionId: 5,
                question: "Who has the highest objective participation?",
                objectiveRate: []
            }
        ]

        for(var i=0; i<players.puuids.length; i++){
            quiz[0].csScore[players.puuids[i]] = players.stats[i].csScore /    players.stats[i].gamePlayed;
            quiz[1].vsScore[players.puuids[i]] = players.stats[i].visionScore / players.stats[i].gamePlayed;
            quiz[2].winRate[players.puuids[i]] = players.stats[i].victory / players.stats[i].gamePlayed;
            quiz[3].quadraKills[players.puuids[i]] = players.stats[i].quadraKills / players.stats[i].gamePlayed;
            quiz[4].objectiveRate[players.puuids[i]] = players.stats[i].objectiveTakenInvolved / players.stats[i].gamePlayed;
        }
        //console.log(quiz);
        resolve(quiz);        
    })
};

标签： javascriptnode.jspromise

解决方案

在这种情况下执行异步过程时会使用 Promise 和回调，因为您所做的是不需要使用 Promise 的简单计算。

这将是您代码的解决方案，欢迎使用 StackOverflow 并快乐编码！

function evaluateQuiz(players) {
    const quiz = [{ ...}]

    for (var i = 0; i < players.puuids.length; i++) {
        // Doing some object changes in this loop like: 
        quiz[0].csScore[players.puuids[i]] = players.stats[i].csScore / players.stats[i].gamePlayed;
    }
    return quiz;
};

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