写流完成后如何返回承诺？

Question

我有一个这样的函数，它创建一个写流，然后将字符串数组写到文件中。写作完成后，我想使它返回Promise。但是我不知道该如何做。

function writeToFile(filePath: string, arr: string[]): Promise<boolean> {
   const file = fs.createWriteStream(filePath);
   arr.forEach(function(row) {
     file.write(row + "\n");
   });
   file.end();
   file.on("finish", ()=>{ /*do something to return a promise but I don't know how*/});
}

感谢您的任何评论！

Answer 1

您将要使用Promise构造函数：

function writeToFile(filePath: string, arr: string[]): Promise<boolean> {
  return new Promise((resolve, reject) => {
    const file = fs.createWriteStream(filePath);
    for (const row of arr) {
      file.write(row + "\n");
    }
    file.end();
    file.on("finish", () => { resolve(true); }); // not sure why you want to pass a boolean
    file.on("error", reject); // don't forget this!
  });
}