在提取函数中使用回调[重复]

Posted 2021-04-27

此问题已经在这里有了答案：

How do I return the response from an asynchronous call?（37个答案）

已关闭21天前。

为什么getscore（）中的i的值（它是第二个api的回调）是非顺序的，导致我的应用程序出现不希望的输出？

function getscore(sid, mid, callback) {
  fetch("https://dev132-cricket-live-scores-v1.p.rapidapi.com/scorecards.php?seriesid=" + sid + "&matchid=" + mid, {
      "method": "GET",
      "headers": {
        "x-rapidapi-host": "dev132-cricket-live-scores-v1.p.rapidapi.com",
        "x-rapidapi-key": "..."
      }
    })
    .then(response => {
      return (response.json());

    })
    .then(function(data2) {
      callback(data2);
    });
}
fetch("https://dev132-cricket-live-scores-v1.p.rapidapi.com/matches.php?completedlimit=6&inprogresslimit=7&upcomingLimit=9", {
    "method": "GET",
    "headers": {
      "x-rapidapi-host": "dev132-cricket-live-scores-v1.p.rapidapi.com",
      "x-rapidapi-key": "..."
    }
  }).then((response) => {
    return response.json();
  }).then((MyJson) => {
      console.log(MyJson);
      for (let i = 0; i < MyJson.matchList.matches.length; i++) {
        //some opeerations
        console.log(i); //sequential
        getscore(matchid, function(data) { //callback second api
          console.log(i); //non-sequential
        });

答案

问题是该API是同步的，并且您正试图以异步方式使用它

您将需要函数getScore返回一个诺言并在您的循环中链接诺言以实现此目标

function getscore(sid, mid) {
    return new Promise(resolve => {
        fetch(
            'https://dev132-cricket-live-scores-v1.p.rapidapi.com/scorecards.php?seriesid=' + sid + '&matchid=' + mid,
            {
                method: 'GET',
                headers: {
                    'x-rapidapi-host': 'dev132-cricket-live-scores-v1.p.rapidapi.com',
                    'x-rapidapi-key': '...'
                }
            }
        )
            .then(response => {
                return response.json();
            })
            .then(function(data2) {
                resolve(data2);
            });
    });
}
fetch(
    'https://dev132-cricket-live-scores-v1.p.rapidapi.com/matches.php?completedlimit=6&inprogresslimit=7&upcomingLimit=9',
    {
        method: 'GET',
        headers: {
            'x-rapidapi-host': 'dev132-cricket-live-scores-v1.p.rapidapi.com',
            'x-rapidapi-key': '...'
        }
    }
)
    .then(response => {
        return response.json();
    })
    .then(async MyJson => {
        console.log(MyJson);

        await Promise.all(
            MyJson.matchList.matches.map(async val => {
                await getscore(matchid);
            })
        );
    });

另一答案

您对getscore方法的调用仅传入2个参数，您的声明调用了3个